109
DLTN9501A-ILT OCTOBER 2015
DLTN9501A-ILT
OCTOBER 2015
ii
This book is designed for instructional use only for authorized Nissan North America, Inc. and Nissan dealer personnel. For additional information contact:
Nissan North America, Inc.Technical TrainingP.O. Box 685001Franklin, TN 37068
© 2015 Nissan North America, Inc.
All rights reserved. No part of this publication may be reproduced in any form without the prior written permission of the publisher.
Printed in U.S.A.
First Printing: October 2015
Nissan North America, Inc.Product, Service, and Technical Training Department
Technical Training
Nissan North America, Inc. reserves the right to alter specifications or methods at any time.
This manual uses post consumer recycled fibers
TEXT
Nissan Titan XD Diesel Technologies Introduction ............................................1
Engine .........................................................................................................................................3
Fuel System ................................................................................................................................................4
Fuel/DEF Filler Caps ................................................................................................................5
Fuel Tank ....................................................................................................................................5
Stage 1 Fuel Filter Housing ...................................................................................................6
Stage 1 Filter .......................................................................................................................7
Lift Pump ...............................................................................................................................7
Stage 2 Fuel Filter Housing ...................................................................................................8
Stage 2 Filter .......................................................................................................................9
Fuel Temperature Sensor .................................................................................................10
Fuel Pressure Sensor ........................................................................................................10
Bosch High Pressure Fuel Pump ..........................................................................................11
Fuel Pump Actuator ...........................................................................................................13
Fuel Rail Supply Lines .............................................................................................................13
Fuel Rails ....................................................................................................................................14
Fuel Rail Pressure Sensor ................................................................................................15
Fuel Pressure Relief Valve ................................................................................................15
Fuel Table Reset .................................................................................................................16
Fuel Injector Supply Lines ................................................................................................16
Fuel Rail Return Line ..........................................................................................................17
Fuel Injectors .............................................................................................................................18
Fuel Injector Installation .....................................................................................................20
Injector Drain Lines ...................................................................................................................22
Constant Pressure Valve ...................................................................................................23
Fuel Injector Driver Circuits ....................................................................................................24
Fuel Rail Pressure Control ......................................................................................................25
0
Clean Care Caps.......................................................................................................................26
Fuel System Testing and Adjustment .................................................................................. 27
Stage 1 Inlet Restriction Test ..........................................................................................27
Stage 2 Filter Restriction Test ........................................................................................28
Stage 2 Drain Line Restriction Test ...............................................................................29
High Pressure Common Rail Actuator Override Test ................................................30
Fuel Injector Return Flow Test ........................................................................................31
Fuel Injector Drain Line Restriction ................................................................................32
High Pressure Fuel System Leak Test ..........................................................................33
Air Management ........................................................................................................................................34
Air Filter ......................................................................................................................................35
Turbocharger Compressor Intake Pressure Temperature Sensor ................................36
Mass Air Flow (MAF) Sensor ................................................................................................36
Fresh Air Flow/Exhaust Gas Recirculation Flow (FAF/EGR Air Flow)....................37
Low Pressure Turbocharger ..................................................................................................38
High Pressure Turbocharger .................................................................................................38
Turbocharger Speed Sensor .................................................................................................39
Low Pressure Turbocharger Boost Pressure Sensor ......................................................39
Compressor Bypass Valve .....................................................................................................40
Compressor Bypass Solenoid ........................................................................................41
Vacuum Pump .....................................................................................................................41
Compressor Bypass Actuator .........................................................................................42
Charge Air Cooler ....................................................................................................................42
Air Intake Connector ................................................................................................................43
Charge Air Cooler Outlet Pressure Temperature Sensor ..............................................43
EGR Temperature Sensor ......................................................................................................44
Intake Air Temperature Sensor .............................................................................................44
1
Exhaust Gas Pressure Sensor ...............................................................................................45
Rotary Turbine Control Valve .................................................................................................46
Rotary Turbine Control Valve Actuator ................................................................................47
Turbocharger Modes of Operation .......................................................................................48
Exhaust Throttle ...................................................................................................................48
Two Stage ............................................................................................................................49
Two Stage Modulated .......................................................................................................50
Single Stage ........................................................................................................................51
Wastegate ............................................................................................................................52
EGR System ................................................................................................................................................53
Exhaust Manifolds and EGR Piping .....................................................................................54
EGR Valve ..................................................................................................................................55
EGR Cooler ...............................................................................................................................56
EGR Cooler Bypass Valve .....................................................................................................57
EGR Flow Calculations ...........................................................................................................57
Exhaust Aftertreatment System .......................................................................................................58
Aftertreatment Overall View ...................................................................................................59
Diesel Oxidation Catalyst (DOC) ..........................................................................................60
Diesel Particulate Filter (DPF) ...............................................................................................61
Decomposition Tube ................................................................................................................62
Selective Catalytic Reduction (SCR) Catalyst ..................................................................62
Ammonia Slip Catalyst (ASC) ...............................................................................................63
Engine Control Module (ECM) ..............................................................................................63
Aftertreatment Sensors ...........................................................................................................64
Intake NOx Sensor .............................................................................................................64
DOC Intake Temperature Sensor ...................................................................................64
DPF Intake Temperature Sensor .....................................................................................65
2
DPF Differential Pressure Sensor ...................................................................................65
DPF Outlet Temperature Sensor ....................................................................................66
SCR Intake Temperature Sensor ...................................................................................66
SCR Outlet Temperature Sensor ...................................................................................67
Outlet NOx Sensor ............................................................................................................67
Diesel Exhaust Fluid (DEF) System .....................................................................................68
Diesel Exhaust Fluid (DEF) ...............................................................................................68
DEF Tank ....................................................................................................................................69
DEF Control Unit ......................................................................................................................70
DEF Quality Sensor .................................................................................................................70
DEF Pump Assembly ...............................................................................................................70
DEF Tank Heater ................................................................................................................71
DEF Temperature Sensor .................................................................................................71
DEF Level Sensor ...............................................................................................................72
DEF Pressure Sensor ........................................................................................................72
DEF Dosing Line Heater ...................................................................................................72
DEF Dosing Valve ....................................................................................................................73
DEF Dosing Conditions ..........................................................................................................73
DEF System States of Operation .........................................................................................74
Priming State .......................................................................................................................74
Dosing State ........................................................................................................................75
Purging State ......................................................................................................................75
DEF Inducements .....................................................................................................................75
DEF Warning Messages....................................................................................................76
Aftertreatment System Operation ........................................................................................78
Soot Oxidation ..........................................................................................................................78
Passive Regeneration ........................................................................................................78
Active Regeneration ..........................................................................................................79
3
Stationary Regeneration ....................................................................................................80
SRC Operation .........................................................................................................................81
Glow Plug System ...................................................................................................................................82
Glow Plugs .................................................................................................................................82
Glow Plug Control Module .....................................................................................................84
Engine Oil ......................................................................................................................................................85
Engine Oil Life Monitor ............................................................................................................85
Transmission & Driveline ..................................................................................................86
Aisin 6-speed Automatic Transmission .......................................................................................86
Transmission Diagnosis and Service ...................................................................................87
Transmission Work Support Quick Learn (Transmission Adjustment) ...................88
Transmission Fail Safe .............................................................................................................88
Transfer Case .............................................................................................................................................89
Front and Rear Axles ..............................................................................................................................90
Suspension ..............................................................................................................................91
Front and Rear Suspension ................................................................................................................91
Wheels and Tires ......................................................................................................................92
Brakes .........................................................................................................................................93
Standard Brake System Features ...................................................................................................93
ABS Actuator and Control Unit ..........................................................................................................94
Trailer Braking ...........................................................................................................................................94
Integrated Trailer Brake Controller .......................................................................................95
Trailer Brake Controls ........................................................................................................96
Steering ......................................................................................................................................97
Steering System ........................................................................................................................97
Heating, Ventilation, and Cooling .................................................................................98
PTC Heater ..................................................................................................................................................98
4
NISSAN TITAN XD DIESEL TECHNOLOGIES INTRODUCTION
The all new, second generation Nissan Titan XD Diesel creates its own position in the highly competitive full size truck segment by combining the diesel capabilities of a 2500 truck with the drivability, affordability, and efficiency of a light duty 1500 truck. The new Titan XD combines outstanding towing and hauling capability with exceptional fuel economy, while offering excellent ride comfort, handling, and interior amenities.
The new Cummins 5.0L V8 Turbo Diesel fills the space between more expensive big bore diesels and less capable smaller displacement diesels. This new engine is standard on the Titan XD Diesel and provides the following:
• 310 hp and 555 lb-ft of torque from a 5.0L dual-stage turbocharged engine
• 45% more torque at cruising speeds than a typical V8 gasoline engine, while providing up to 20% better fuel economy when hauling full loads
• Quiet, responsive, and quick starting through the use of a Bosch high-pressure common rail fuel system with glow plugs
• Lightweight, but stronger compacted graphite iron engine block with aluminum cylinder heads and 32-valve DOHC design
• EGR cooling and comprehensive exhaust aftertreatment system for clean emissions
Nissan Titan XD Diesel Technologies Introduction 1
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2 Nissan Titan XD Diesel Technologies Introduction
ENGINE
The Cummins 5.0L V8 Turbo Diesel engine is an exciting addition to the Titan XD. This diesel engine is powerful, quiet, and clean thanks to innovative components and advanced electronic controls. This section introduces the major systems and components that are new for the Cum-mins engine.
Engine 3
Fuel System
The fuel system on the Cummins 5.0L V8 Turbo Diesel engine includes low pressure, high pres-sure, and return paths. The following information introduces the main components of the fuel delivery system and traces the flow of fuel from the fuel tank to the injectors, and back to the fuel tank.
Components are presented in the order of flow from the fuel tank to the injectors and back to the fuel tank.
4 Engine
Fuel/DEF Filler Caps
Fuel and Diesel Exhaust Fluid (DEF) filler caps are located on the left side of the vehicle. The fuel cap is green and the DEF cap is blue.
Fuel Tank
The fuel tank is located under the vehicle near the left frame rail. The tank houses diesel fuel but does not contain a fuel pump.
Diesel Fuel DEF
Engine 5
Stage 1 Fuel Filter Housing
The stage 1 fuel filter housing is located just in front of the fuel tank. The stage 1 fuel filter hous-ing includes the following components:
• 5-micron fuel filter with replaceable O-ring: filters particles and water from the fuel
• 12-volt fuel lift pump: supplies low-pressure fuel to the stage 2 filter housing and high pres-sure fuel pump
• Water in Fuel (WIF) sensor: detects the presence of water in the bottom of the stage 1 fuel filter housing and illuminates an icon in the combination meter
• Water/fuel separator drain valve: 1/4-turn drain valve used for draining unwanted water from the filter housing
• Thermal recirculating valve: when fuel is cold, this valve redirects fuel back to the unfiltered side of the stage 1 fuel filter housing rather than to the fuel tank
• Pressure relief valve to protect the 12-volt lift pump
WIF SensorWater/Fuel Separator Drain
From Fuel TankTo Stage 2 Filter
From Stage 2 Filter To Fuel Tank
Thermal Recirculating Valve
6 Engine
Stage 1 Filter
The stage 1 fuel filter must be installed for the lift pump to deliver fuel to the stage 2 fuel filter. This safeguard was designed into the filter and housing to prevent unfiltered fuel from damaging critical fuel system components. The stand pipe inside the stage 1 filter housing includes a check ball and a conical relief. The fuel filter includes a pintle that seats in the relief when the filter is installed. When the pintle seats, the check ball is moved away from the fuel pump inlet and fuel can flow to the stage 2 filter housing. If the filter is not in place, the check ball seals the pump inlet
For stage 1 fuel filter change intervals, refer to the Owner’s Manual or the MA section of the ESM.
Lift Pump
Whenever the ignition is cycled ON, the lift pump operates for approximately one minute to prime the fuel system. Normal lift pump supply pressure is approximately 51 to 87 psi (3.5 to 6 bar) (350 to 600 kPa absolute) with the engine cranking or running.
Engine 7
Stage 2 Fuel Filter Housing
The stage 2 fuel filter housing is mounted on the intake manifold at the left side of the engine. This assembly also serves as a supply and return manifold for fuel. The stage 2 fuel filter housing includes the following components:
• 3-micron fuel filter with replaceable O-ring: filters particles in the fuel
• Fuel Pressure Sensor: senses lift pump pressure in the stage 2 filter housing after the filter
• Fuel Temperature Sensor: senses the temperature of fuel to help calculate fuel delivery requirements based on viscosity
Fuel Temperature Sensor
Fuel Pressure Sensor
Injector Return
Fuel Rail Drain
High Pressure Pump Supply
Fuel From Stage 1 Housing
Fuel Rail and Pump Return
High Pressure Pump Return(Not Visible)
8 Engine
Stage 2 Filter
The stage 2 fuel filter is a 3-micron filter. The stage 2 filter element features a supply/return seal that keeps the supply fuel in the upper sections of the filter housing from the return fuel pas-sages in the bottom. If the filter or seal is not installed or seated correctly, the engine will fail to start because fuel will flow directly back out of the fuel drain line port and back to the stage 1 return port.
When installing a new filter:
• Lubricate the inner seal of the filter
• Lubricate and install a new filter cap O-ring
• Insert the filter onto the stand pipe first
• Press the filter down until seated and then screw the cap down after the filter is properly seated
If the seal is damaged and cannot seal the housing chambers correctly, a poor performance or no-start condition may occur.
For stage 2 fuel filter change intervals, refer to the Owner’s Manual or the MA section of the ESM.
Engine 9
Fuel Temperature Sensor
The fuel temperature sensor measures fuel temperature before it passes through the stage 2 fuel filter housing. This sensor is critical for determining if fuel temperature is within specifica-tions If fuel temperature is above specifications, a fault code could be set and engine power may be reduced to protect the engine.
Fuel Pressure Sensor
The fuel pressure sensor monitors the pressure of the fuel after the stage 2 filter and before it enters the high pressure fuel pump to ensure there is sufficient pressure to sustain fuel delivery. The ECM continuously monitors fuel pressure and will set a fault code if fuel pressure falls below a certain threshold.
When measuring fuel pressure in CONSULT, remember that the pressure is shown as an absolute value. To obtain the actual pressure, the current atmospheric pressure must be subtracted from this value. Fuel pressure is listed as “FUEL SPLY PRESS” on CONSULT.
10 Engine
Engine 11
Bosch High Pressure Fuel Pump
The high pressure fuel pump is located at the front of the engine valley. The 2-cylinder pump is sealed to the cylinder block with bolts and an O-ring and is driven by a chain and sprocket at a 1:1 ratio to the crankshaft. The fuel pump is timed from the factory and includes an alignment key that is turned to the 2 o’clock position when cylinder 1 is at TDC.
Fuel Pump Actuator
Fuel Supply from Stage 2
Fuel Return (Pump Drain)
The high pressure fuel pump is the first component in the high pressure side of the fuel system. The pump can generate fuel pressures up to 29,000 psi (2,000 bar) under high-load operation. When filtered fuel from the stage 2 filter enters the pump, it is either pumped to the fuel rail or delivered back to the stage 2 fuel filter housing, depending on fuel pressure needs. A cascade overflow valve within the pump regulates fuel for lubrication and regulates fuel to the fuel pump actuator and to the fuel return. A high pressure check valve within the pump keeps high pressure from damaging the pump.
Cascade Overflow Valve
High Pressure Check ValveFuel Pump Actuator
12 Engine
Fuel Pump Actuator
The fuel pump actuator is located on top of the high pressure fuel pump and is sometimes called the volume control valve. The fuel pump actuator is a normally open, pulse-width modulated (PWM) valve used to control fuel volume into the high pressure fuel pump. The ECM controls operation of the fuel pump actuator and fuel pressure relief valve to regulate fuel rail volume and pressure. The fuel pump actuator and O-rings are the only serviceable components on the high pressure fuel pump.
Fuel pump actuator operation will be covered in the Fuel Rail Pressure Control topic.
Fuel Rail Supply Lines
High pressure fuel exits the fuel pump at each pump cylinder and travels in individual lines to the right bank fuel rail. Fuel fills the right bank fuel rail and is then transfered to the left bank fuel rail through a rail-to-rail supply line. Whenever high pressure fuel lines are loosened or removed and installed, the fuel system must be primed and then a high pressure fuel system leak test must be performed.
Rail-to-Rail Supply Line
Fuel Pump Outlet
Two Right Bank Supply Lines from Fuel Pump
Engine 13
Fuel Rails
The left and right fuel rails serve as manifolds for high pressure fuel, accumulating and distribut-ing fuel to each fuel injector supply line. Key components that are located on the fuel rails include:
• Fuel rail pressure sensor: located at the front of the right fuel rail
• Fuel pressure relief valve: located on the back of the left fuel rail
• Fuel injector supply lines: eight fittings spaced throughout each fuel rail
• Fuel rail return line: located near the back of the left fuel rail
Fuel RailPressureSensor
Fuel PressureRelief Valve
Fuel Rails
Fuel InjectorSupply Lines(8 total)
Fuel RailReturn Line
14 Engine
Fuel Rail Pressure Sensor
The fuel rail pressure sensor monitors the fuel pressure within the fuel rails and communicates this data to the ECM. The ECM uses fuel pressure data to adjust the PWM signal to the fuel pump actuator and fuel pressure relief valve to achieve the desired fuel pressure for optimum fuel injection.
Fuel Pressure Relief Valve
The fuel pressure relief valve is a normally open, PWM valve. The ECM monitors fuel rail pres-sure sensor data and adjusts the PWM signal to the fuel pump actuator and fuel pressure relief valve to maintain the desired fuel pressure. The fuel pressure relief valve can bleed excess fuel rail pressure from the rails through the fuel rail return line, back to the stage 2 fuel filter housing.
When the engine is turned off, the fuel pressure relief valve opens, allowing fuel pressure inside the rail to depressurize. It may take up to 10 minutes for high pressure to bleed down enough to service high pressure fuel system components.
No PWM signal PWM signal
Engine 15
Fuel Table Reset
If the fuel rail pressure sensor or fuel pressure relief valve is replaced, the fuel table reset procedure must be performed with CONSULT. The fuel table reset will reset the data tables for corresponding components to factory default values (unlearned values).
Fuel Injector Supply Lines
Fuel injector supply lines carry high pressure fuel from the fuel rails to the supply fittings on the fuel injectors. Each supply line includes a vibration isolator to enhance durability. Always note the position of the fuel injector supply line prior to removal so it can be installed in the same ori-entation. As with all fuel system fittings, ports should be capped for the duration of the repair to prevent debris from entering the fuel system. When installing a fuel injector supply line, hand tighten the fittings first and then torque to specification. Finally, perform the high pressure fuel system leak test to make sure the system does not leak.
16 Engine
Fuel Rail Return Line
A fuel rail return line is located between the left fuel rail and the stage 2 fuel filter housing. When the ECM determines that fuel pressure should be reduced in the fuel rails, the fuel pressure relief valve allows fuel in the rail to be drained to the stage 2 fuel filter housing (return manifold) through the fuel rail return line.
If the fuel rail return line becomes restricted, a no-start condition may occur. If the fuel system cannot control fuel rail pressure by bleeding fuel from the rails, fuel flow will stop.
Fuel Rail Return Line
Engine 17
Fuel Injectors
The Cummins 5.0L Turbo Diesel engine uses eight Bosch piezoelectric fuel injectors to supply atomized fuel to the cylinders for combustion. Fuel is supplied to the top of the injector and return fuel is directed back to the stage 2 filter housing through a return line.
Injector hold-down clamps are used to secure pairs of adjacent injectors. Each injector includes a replaceable O-ring and a replaceable sealing washer where the injector seals in the cylinder head. A special tool must be used to remove the injectors without damage.
Supply Return
O-ring
Sealing Washer
Injector Hold-down Clamp
18 Engine
Piezoelectric injectors require electrical current, high pressure fuel, low pressure fuel, and reversed electrical current to inject fuel and close the injector after injection. Piezoelectric injec-tors use high and low fuel pressure within the injector and piezo crystals within a stack of ceramic discs. High pressure fuel near the top of the high pressure control chamber holds the injector needle in place until it is time to inject. When the ECM sends current through the piezo stack, the piezo crystals expand. This expansion is amplified by the hydraulic pressure of the fuel in the low pressure chamber to move the control valve. High pressure fuel in the control cham-ber exits to the low pressure chamber when the control valve opens. This action unseats the injector needle and fuel is injected. To close the injector, current must flow in the opposite direc-tion (reverse polarity) to retract the piezo crystals and allow fuel pressure in the injector to seat the injector needle.
NOTE: Never disconnect the injector electrical connector while the engine is running. If the injector driver circuit is not able to reverse polarity on the circuit after injection, the injector may become stuck in the open position.
High Pressure Fuel
High Pressure
Injector Needle
Control Valve
Low Pressure Chamber
Control Chamber
Engine 19
Fuel Injector Installation
When installing a new fuel injector, note the following:
• Each injector has a unique 8-character alphanumeric code stamped on the top of the injec-tor. This trim code is set during production and corresponds to the specific flow characteris-tics of the injector. This code must be entered in CONSULT as an Engine Work Support procedure if a new injector is installed.
- Fuel Table reset is included in the procedure for injector code entry
20 Engine
• Perform a resistance measurement on the new injector before installation to verify it is within specified values
• Install a new O-ring on the injector before installing
• Make sure the sealing washer from the old injector is not in the injector bore. If more than one sealing washer is used, improper sealing or performance issues may occur
• Use the injector bore brush to clean the cylinder head where the injector will be installed, and then remove any debris
• Install a new injector return O-ring
• Left bank injectors: Install injectors with their electrical connectors facing the back of the engine
• Right bank injectors: Install injectors with their connectors facing the front of the engine
• Perform the high pressure fuel system leak test after installation
Engine 21
Injector Drain Lines
Excess fuel from the injector control chamber dumps out of the return port on the injector and into the injector drain line. Each bank of injectors has its own injector drain line. The two drain lines meet at the constant pressure valve on the left side of the engine near the stage 2 fuel filter housing.
22 Engine
Constant Pressure Valve
During normal operation, the injectors continuously release fuel from the control chamber with each injection into the cylinder. This fuel pressure pushes on a check ball inside the constant pressure valve as the pressure in the line increases to the point necessary to move the ball off its seat. At this point, some of the fuel passes into the stage 2 fuel filter housing, gets filtered again and is delivered back to the high pressure fuel pump.
At startup and system priming, the constant pressure valve allows the fuel to flow in the opposite direction from the stage 2 filter housing directly up to the low pressure chamber of the piezoelectric injector so the injectors will quickly receive sufficient backpressure to open the control valve. A pinched line anywhere in the injector drain line can cause backpressure to become higher than normal since the injectors cannot dump off the excess fuel inside the control chamber. Over-pressurization of the injector drain line can cause damage to the fuel injectors.
The constant pressure valve is a permanent part of the injector return line and is not serviceable separately.
Maintaining Injector Backpressure
Bleeding Injector Backpressure
Injector Drain Lines
ConstantPressureValve
Engine 23
Fuel Injector Driver Circuits
The ECM includes two individual injector driver circuits and two internal DC to DC converters. These converters step the 12-volt feed from the battery up to 170 volts when the injectors are connected. Each converter controls four injectors, with each driver controlling every other injec-tor in the firing order. Immediately following injection, the polarity of the injector circuit is reversed, allowing the piezo stack to retract.
The injector driver circuit is set up so that companion cylinders are on the same group of injec-tors on the driver circuit. The circuit is designed to supply the 250 volts to only a single group of injectors at one time so that a short in one of the groups will not adversely affect the other group. When the circuit is operating with the piezoelectric injectors connected, the circuit will supply 170 volts with amperage as high as 19 amps. However, if the injector is disconnected, the volt-age can be as high as 250 volts. It is never advised to disconnect piezoelectric injectors while running as engine damage or physical injury can occur.
Primary inputs for injection include the accelerator pedal sensor input (driver) and the crankshaft position sensor. After the ECM determines top dead center of cylinder number 1 on the com-pression stroke at startup (using the camshaft position sensor), the ECM then relies on the crankshaft position sensor to control the timing of the injections. A variety of other inputs affect injection timing and volume, such as charge air cooler outlet pressure, coolant temperature, and speed/load conditions. At least 150 rpm and a minimum rail pressure of 1800 psi is necessary for the engine to start.
24 Engine
Fuel Rail Pressure Control
The ECM controls fuel rail pressure by opening, closing, or modulating the fuel pump actuator and fuel pressure relief valve. Various fueling modes are available based on engine load, tem-peratures, and pressures. The following fueling modes are available:
• Startup: This mode is used until fuel temperature reaches approximately 70° F. The ECM modulates the fuel pressure relief valve while allowing the fuel pump actuator to stay open.
• Low Idle: The ECM modulates the fuel pump actuator and fuel pressure relief valve as needed to achieve the desired fuel rail pressure.
• High Idle/Load: This mode is used under high load conditions. The ECM closes the fuel pressure relief valve to help build fuel pressure for additional fuel delivery needs. The ECM modulates the fuel pump actuator as necessary to maintain a higher fuel pressure.
Full Open = Electrically OFF
Full Close = Electrically ON
Modulated = Pulse Width ON/OFF
(PRESS)
(BOTH)
(VOL)
Engine 25
Clean Care Caps
Whenever components are removed for testing, orifices should be immediately covered with clean care caps to prevent debris from entering the openings. A full assortment of clean care caps are available for fuel and air management system orifices. These caps are included as essential service tools for the Titan XD Diesel.
26 Engine
Fuel System Testing and Adjustment
There are a number of fuel system tests and procedures that can help in diagnosing no-start, hard-start, and performance concerns. The following information summarizes some of these available tests. Always refer to Service Information for detailed steps and precautions.
Stage 1 Inlet Restriction Test
This test checks for a fuel restriction between the fuel tank and the stage 1 fuel filter housing.
1. Disconnect the hose fitting at the stage 1 fuel filter housing inlet.
2. Insert a hose and pressure transducer into the stage 1 fuel filter housing inlet.
3. Turn the ignition ON to prime the fuel system.
4. Start the engine and allow it to idle.
5. Check for air bubbles in the clear hose. Air bubbles indicate a leak is present and the fuel supply hose may be damaged.
6. The pressure transducer should indicate less than 3 psi of vacuum (-3 psi) or -20 kPa (6” Hg)
7. If vacuum is greater than this specification, a restriction exists
Engine 27
Stage 2 Filter Restriction Test
This test checks for a restriction in the stage 2 fuel filter housing.
NOTE: The fuel pressure sensor monitors fuel pressure after it has passed through the stage 2 fuel filter.
NOTE: CONSULT displays fuel supply pressure as an absolute value. You must account for atmospheric pressure when interpreting this pressure reading.
To test for a filter restriction, perform the following:
1. Disconnect the hose fitting at the stage 2 fuel filter housing inlet.
2. Insert a hose and pressure transducer into the stage 2 fuel filter housing inlet.
3. Turn the ignition ON to prime the fuel system.
4. Connect CONSULT and monitor the fuel supply pressure.
5. Start the engine and allow it to idle.
6. Compare the pressure transducer value to the fuel supply pressure value in CONSULT.
7. After adjusting for atmospheric pressure, the pressure difference should be 5 psi (34 kPa) or less.
8. A greater difference in pressure indicates a restriction in the stage 2 fuel filter.
28 Engine
Stage 2 Drain Line Restriction Test
This test for a restriction in the drain line from the stage 2 fuel filter housing back to the fuel tank.
1. Install a pressure transducer at the stage 2 fuel filter housing drain line.
2. Calibrate the transducer to atmospheric pressure before beginning the test.
3. Make sure the fuel system is primed before attempting to start the engine.
4. If the engine will not start, measure pressure while cranking.
5. If the engine starts, idle for one minute before checking the pressure.
6. If drain line pressure is more than 15 psi (1 bar), there is a restriction in the return line to the stage 1 fuel filter housing and/or the return line to the fuel tank.
Engine 29
High Pressure Common Rail Actuator Override Test
Recall that the fuel pump actuator and the fuel pressure relief valve work in conjunction to con-trol fuel rail pressure. If the fuel pump actuator cannot properly control the amount of fuel into the high pressure pump, or the fuel pressure relief valve cannot control the flow of fuel out of the fuel rails, sufficient fuel pressure cannot be achieved. If either of these components is faulty, the vehi-cle may not be able to start or run.
The high pressure common rail actuator override test is used to test the operation of these two components.
1. With the engine off, remove the banjo bolt that fastens the fuel rail return line at the fuel pressure relief valve.
2. Install the Fuel System Leak Tester hose (J-54431) into this fitting.
3. Place the open end of the hose into a suitable container.
4. Turn the ignition ON.
5. Fuel will flow for about one minute while the fuel system primes.
6. Use CONSULT, Active Test to select the HPCR ACT Override test.
7. Perform each test from the list and note the flow of fuel into the container during each pro-cedure.
8. When the fuel pump actuator is commanded closed, fuel should stop flowing into the con-tainer. This confirms the operation of the fuel pump actuator.
9. Reset the test and then command the fuel pressure relief valve closed. Fuel should stop flowing into the container when the valve is closed. This confirms the operation of the fuel pressure relief valve.
NOTE: Refer to the Job Aid at the back of this book for HPCR ACT Override details.
30 Engine
Fuel Injector Return Flow Test
The fuel injector return flow test is used to determine if one or more fuel injectors has excessive drainage compared to other injectors on the same bank. This test requires a special tool that can be purchased through TechMate. This tool contains four individual constant pressure valves that must be connected to each injector return line.
1. Disconnect the injector return lines from all four injectors on one bank.
2. Plug the injector return line hose at each of the four fittings.
3. Install the constant pressure valve hoses on the four injectors.
4. Place the graduated cylinders on a flat surface and verify all connections.
5. Start the engine and allow it to idle while observing the quantity of fuel flowing into the cyl-inders.
6. If the quantity of fuel flowing out of the injector return on one injector is greater than the others, refer to specifications to determine if the injector is faulty.
7. If the engine does not start, a cranking test can be performed. The smaller, lower portion of the containers is used for the cranking test.
8. Replace all injector return O-rings before installing the return line.
Engine 31
Fuel Injector Drain Line Restriction
This test checks for fuel injector drain line restrictions on each bank of cylinders.
1. Disconnect the injector return lines from all four injectors on one bank.
2. Plug the injector drain line connections for 3 of the 4 injectors.
3. Insert the remaining drain line into a suitable container.
4. Use CONSULT to run the electric lift pump test.
5. If a steady stream of fuel flows from the drain line, there is no drain line restriction on this bank.
6. Repeat the test for the other bank.
32 Engine
High Pressure Fuel System Leak Test
Anytime the high pressure side of the fuel system is opened for diagnosis or service, the Fuel System Leak Test should be performed. This Active Test slowly ramps fuel rail pressure up to 29,000 psi (2,000 bar) to test for high pressure leaks.
NOTE: After initiating this test, do not remain in the vicinity of the high pressure fuel system. Let the test complete and then return to check for residual fuel.
Engine 33
Air Management
The Cummins 5.0L V8 Turbo Diesel engine uses advanced dual-stage turbocharging and Exhaust Gas Recirculation (EGR) systems to provide outstanding driveability and for contribu-tions to an effective exhaust aftertreatment system.
The diagram above shows an overall view of air, EGR, and exhaust flow through the engine. This section covers the details of the air management and EGR systems. Items are presented in the order of flow from the air filter to the beginning of the aftertreatment system.
34 Engine
Air Filter
The air filter is located within the air filter box on the left side of the engine compartment. The air filter filters all ambient air entering the engine. Because the Cummins 5.0L V8 Turbo Diesel engine does not use a conventional intake throttle body to regulate air flow into the engine, the air filter serves a critical role in providing a significant amount of clean, unrestricted air to the engine. The engine should NEVER be operated without the air filter or air intake duct installed.
In addition, the air intake system has a specification for the allowable restriction to air flowing across the air filter.
• Maximum Intake Restriction: Clean Air Filter - 234 mm H2O or 10 inches H2O
• Maximum Intake Restriction: Dirty Air Filter - 635 mm H2O or 25 inches H2O
Air filter maintenance is critical. If the air filter becomes too dirty, it can cause an excessive restriction. Excessive air filter restriction can lead to serious problems including:
• Oil leakage from the turbocharger seals into the fresh air stream
• Negative pressure in the engine crankcase, leading to an unmetered source of oil entering the combustion chambers
• Smoke in the exhaust stream and damage to aftertreatment system components
Engine 35
Turbocharger Compressor Intake Pressure Temperature Sensor
The turbocharger compressor intake pressure temperature sensor is located on top of the air fil-ter housing. This sensor monitors the temperature and pressure of air in the intake air duct, and can help the ECM determine air filter restriction and changes in altitude.
Mass Air Flow (MAF) Sensor
The MAF sensor is located on the intake air duct just after the air filter housing. The ECM uses data from the MAF sensor and other air intake sensors to determine the quantity of air entering the engine. In addition, the MAF sensor has a major impact on EGR calculations and Selective Catalytic Reduction (SCR) dosing.
Turbocharger Compressor Intake Pressure Temperature Sensor
MAF Sensor
36 Engine
Fresh Air Flow/Exhaust Gas Recirculation Flow (FAF/EGR Air Flow)
When viewing data on CONSULT, “FAF/EGR AIR FLOW” is a Data Monitor item that represents and ECM calculation of mass air flow and EGR flow combined. When EGR is not flowing (both EGR valves closed), data monitor values for MAF and FAF/EGR AIR FLOW should be similar. Whenever EGR is flowing into the air intake connector, FAF/EGR flow values will be higher than MAF values due to EGR being added to the fresh air.
Engine 37
Low Pressure Turbocharger
The low pressure turbocharger is located in the engine valley below the intake manifold. The low pressure turbocharger is the larger of two turbochargers and is the primary supplier of boost pressure to the engine. The low pressure turbocharger housing contains the rotary turbine control valve that will be discussed in detail later in this section.
High Pressure Turbocharger
The high pressure turbocharger is connected to the back of the low pressure turbocharger. The high pressure turbocharger is a smaller turbo that spins at higher speeds than the low pressure turbocharger. The high pressure turbocharger is used to reduce “turbo lag” at low engine speeds when boost is needed quickly.
Low PressureTurbocharger
High PressureTurbocharger
38 Engine
Turbocharger Speed Sensor
The turbocharger speed sensor is located on the top of the high pressure turbocharger com-pressor housing. This sensor monitors the rotational speed of the high pressure turbocharger to protect against over-speed conditions.
Low Pressure Turbocharger Boost Pressure Sensor
The low pressure turbocharger boost pressure sensor is located on the compressor outlet side of the low pressure turbocharger. This sensor monitors charge air pressure in the compressor outlet tubing.
High PressureTurbocharger
Turbocharger SpeedSensor
Low PressureTurbocharger BoostPressure Sensor
Engine 39
Compressor Bypass Valve
The compressor bypass valve is located in the low pressure turbocharger compressor outlet tube. This valve is normally closed when the engine is off and during low engine speeds when boost is needed quickly (Two Stage mode). When closed, air is directed through the low pres-sure turbocharger and into the high pressure turbocharger compressor to build boost quickly. When opened, the compressor bypass valve creates a direct path for compressed air from the low pressure turbocharger to flow to the charge air cooler (all other turbocharger modes). The valve is not a variable position valve; it is either fully open or fully closed.
40 Engine
Compressor Bypass Solenoid
The compressor bypass solenoid is located on the front left portion of the front gear cover. The compressor bypass solenoid is an ON/OFF solenoid that is controlled by the ECM. When ener-gized by the ECM, the compressor bypass solenoid directs vacuum to the compressor bypass actuator to open the compressor bypass valve.
Vacuum Pump
The vacuum pump is located on the front of the engine and is driven by the fan belt. The vacuum pump provides vacuum to the compressor bypass solenoid.
Vacuum PumpCompressorBypassSolenoid
Engine 41
Compressor Bypass Actuator
The compressor bypass actuator is located below the turbocharger compressor outlet tube. Vacuum from the compressor bypass solenoid moves the compressor bypass valve in the com-pressor outlet tube.
Charge Air Cooler
The charge air cooler is located between the radiator and the condenser. The charge air cooler cools the compressed charge air before it enters the air intake connector.
Compressor BypassActuator
Charge Air Cooler
42 Engine
Air Intake Connector
The air intake connector is located on the top of the engine. Cooled charge air from the charge air cooler enters the air intake connector. Cooled or uncooled EGR also enters the air intake connector and is combined with charge air before entering the air intake manifold.
Charge Air Cooler Outlet Pressure Temperature Sensor
The charge air cooler pressure temperature sensor is located on the top front of the air intake connector. The charge air cooler outlet pressure temperature sensor measures the charge air pressure and temperature after it exits the charge air cooler and before EGR is mixed.
Air Intake Connector
Air Intake Manifold
Charge Air Cooler OutletPressure Temperature Sensor
Engine 43
EGR Temperature Sensor
The EGR temperature sensor is located on the front underside of the air intake connector. This sensor measures EGR gas temperature before it is mixed with intake charge air. The EGR Tem-perature sensor is used for:
• EGR cooler bypass and cooled EGR control
• EGR flow calculations
• EGR cooler efficiency calculations
• EGR cooler protection
Intake Air Temperature Sensor
The intake air temperature sensor is located on the left side of the air intake connector, just before the air intake manifold. This sensor measures the temperature of the combined charge air and EGR before it enters the intake manifold. This is the last air temperature reading the ECM receives before air enters the combustion chambers.
44 Engine
Exhaust Gas Pressure Sensor
The exhaust gas pressure sensor is remotely located at the back left corner of the air intake manifold. The sensor is mounted in a tube that reads exhaust gas pressure from the left exhaust manifold. The exhaust gas pressure sensor is used as an input for rotary turbine control valve positioning during cold start and is also used to assist in thermal management for the aftertreat-ment system. In addition, the exhaust gas pressure sensor is used by the ECM as one of the inputs to determine the quantity of EGR flow.
Engine 45
Rotary Turbine Control Valve
The rotary turbine control valve is located within the low pressure turbocharger housing. This variable-position valve is moved by a linkage on the rotary turbine control valve actuator. The rotary turbine control valve can direct exhaust gases through various paths to support the vari-ous turbocharger modes, including:
• Exhaust Throttle
• Two Stage
• Two Stage Modulated
• Single Stage
• Wastegate
Rotary Turbine Control Valve
46 Engine
Rotary Turbine Control Valve Actuator
The rotary turbine control valve actuator is located at the top rear portion of the air intake mani-fold. The rotary turbine control valve actuator controls the position of the rotary turbine control valve based on commands from the ECM. The actuator assembly also includes a sensor that monitors the position of the rotary turbine control valve actuator. This position information is used by the ECM for control of the rotary turbine control valve.
If the rotary turbine control valve actuator or linkage is replaced, the actuator must be calibrated using CONSULT. This procedure uses CONSULT and the internal position sensor within the actuator to calibrate the actuator and linkage.
Engine 47
Turbocharger Modes of Operation
The ECM controls the positions of the compressor bypass valve and rotary turbine control valve to produce different turbocharger modes, depending on the driving condition or aftertreatment system needs. The following pages describe these different turbocharger modes.
Exhaust Throttle
Exhaust Throttle mode is used at lower engine speeds and lower torque situations. During Exhaust Throttle mode, air enters the low pressure turbocharger compressor. The compressor bypass valve is closed. Air travels into, and is compressed in the high pressure turbocharger compressor because it is the only path for air flow when the compressor bypass valve is closed. The rotary turbine control valve is positioned to restrict exhaust flow. This creates heat for the aftertreatment system during regeneration, drives additional EGR into the intake manifold, and provides a faster engine warmup.
48 Engine
Two Stage
Two Stage operation is used when boost pressure is needed quickly, such as high load condi-tions off idle. During Two Stage mode, air enters the low pressure turbocharger compressor. The compressor bypass valve is closed. Air travels into, and is compressed in the high pressure turbocharger compressor because it is the only path for air flow when the compressor bypass valve is closed. The rotary turbine control valve directs all exhaust flow to the high pressure tur-bocharger turbine first, and then to the low pressure turbocharger turbine. The high pressure turbocharger spins, producing boost quickly to eliminate turbo lag.
Engine 49
Two Stage Modulated
Two Stage Modulated operation occurs when transitioning between Two Stage and Single Stage operation. When Two Stage Modulated operation is needed, the compressor bypass valve opens. When the compressor bypass valve opens, the path of least resistance becomes the passage from the low pressure turbocharger compressor to the charge air cooler. The rotary turbine control valve directs exhaust flow in varying proportions to both high and low pressure turbocharger turbines.
50 Engine
Single Stage
Single Stage operation occurs when maximum boost is needed for higher speeds or high loads when the high pressure turbocharger can no longer supply sufficient air volume to achieve desired boost. During Single Stage operation, the compressor bypass valve remains open, allowing unrestricted air flow from the low pressure turbocharger to the charge air cooler. The rotary turbine control valve directs full exhaust flow to the low pressure turbocharger turbine with only residual exhaust gas exposed to the high pressure turbocharger turbine.
Engine 51
Wastegate
Wastegate operation is used to limit boost pressure. During Wastegate operation, the compres-sor bypass valve remains open, allowing unrestricted air flow from the low pressure turbo-charger to the charge air cooler. The rotary turbine control valve directs exhaust flow directly to the aftertreatment system, bypassing both turbines.
52 Engine
EGR System
The EGR system is designed to reduce oxides of nitrogen (NOx) in the exhaust stream that results from diesel combustion. The following information describes the function of EGR compo-nents and EGR operation.
EGR Cooler
EGR Valve
EGR Cooler
Exhaust Manifold
Exhaust Manifold
Bypass Valve
Engine 53
Exhaust Manifolds and EGR Piping
After combustion, exhaust gases exit the combustion chambers through the exhaust manifolds and enter the EGR piping. Exhaust gases can take three distinct directions, depend-ing on which is the path of least resistance. The ECM controls the positions of the rotary turbine control valve, EGR valve, and EGR cooler bypass valve to determine the paths that exhaust gas takes.
To EGR CoolerEGR Cooler Bypass
To Aftertreatment System
Rotary TurbineControl ValveInlet
54 Engine
EGR Valve
The EGR valve is located on the right side of the engine at the back of the EGR cooler. The ECM varies the position of the EGR valve to regulate the amount of exhaust gas that enters the EGR cooler from the right bank EGR pipe. The EGR valve includes an internal sensor that pro-vides EGR valve position to the ECM. The EGR valve may close under certain conditions like cold start, low engine speeds or loads, or if active EGR fault codes are present.
EGR Valve
EGR Cooler
Exhaust Enters
Engine 55
EGR Cooler
The EGR cooler is located on the right side of the engine just outside the air intake manifold. The EGR cooler assembly includes a cast iron coolant manifold that secures the cooler to the air intake manifold. The EGR cooler receives engine coolant from the water pump and circulates coolant through the manifold and cooler to lower the temperature of exhaust gases before they are recirculated into the combustion chamber as cooled EGR. When EGR gases are cooled, combustion temperatures are lowered, and as a result, NOx levels are also lowered.
Coolant flows through the EGR cooler in the same direction as exhaust gas flow. The EGR valve is also cooled by engine coolant.
EGR Cooler Bracket (Manifold)
EGR CoolerInternal View
56 Engine
EGR Cooler Bypass Valve
The EGR cooler bypass valve is located behind the air intake connector. The EGR cooler bypass valve allows EGR to be diverted around the EGR cooler and directly into the charge air stream when conditions are required (cold start, regeneration, or times when combustion tem-peratures must be raised.) The EGR cooler bypass valve includes an internal sensor that com-municates EGR cooler bypass valve position to the ECM. The EGR cooler bypass valve is also cooled by engine coolant.
EGR Flow Calculations
During Exhaust Throttle mode, the ECM closes the EGR valve and opens the EGR cooler bypass valve to prevent EGR cooling. This is done to heat the engine quicker during cold start and for regeneration. For all other turbocharger modes, the ECM opens or closes the EGR valve and EGR cooler bypass valve as needed based on pressures and temperatures.
The ECM compares the charge air cooler outlet pressure sensor and exhaust gas pressure sen-sor measurements to help determine the EGR flow relative to the position sensors in the EGR valve and EGR cooler bypass valve. The ECM also uses the EGR temperature sensor to deter-mine the temperature of EGR gases before they mix with charge air. If this temperature is too high, the ECM may command the EGR valve closed to protect the EGR cooler from high tem-perature damage.
The ECM also uses the air intake manifold temperature sensor to calculate EGR entering the air intake manifold prior to combustion. CONSULT data monitor item “FAF/EGR AIR FLOW” dis-plays the combination of mass air flow and EGR air flow combined.
Engine 57
Exhaust Aftertreatment System
The term “exhaust aftertreatment” refers to the use of additional components in the exhaust sys-tem that help produce chemical reactions to reduce harmful tailpipe emissions. It also includes many sensors that help determine system operation and evaluate the effectiveness of the system in reducing these emissions.
The aftertreatment system is primarily used to reduce Particulate Matter (PM) and oxides of nitrogen (NOx) emissions. PM may also be referred to as soot.
The front of the aftertreatment system includes the Diesel Oxidation Catalyst (DOC), Diesel Par-ticulate Filter (DPF), and various sensors that measure temperatures, pressures, and incoming NOx content. Soot is oxidized in this front portion of the system.
The second part of the aftertreatment system includes the decomposition tube, Diesel Exhaust Fluid (DEF) dosing valve and associated components for DEF dosing, Selective Catalytic Reduction (SCR) catalysts, Ammonia Slip Catalyst (ASC), and various sensors that measure temperatures, pressures and outgoing NOx content. NOx is significantly reduced in this second part of the aftertreatment system.
58 Engine
Aftertreatment Overall View
1. Intake NOx Sensor
2. Diesel Oxidation Catalyst (DOC) Intake Temperature Sensor
3. Diesel Oxidation Catalyst (DOC)
4. Diesel Particulate Filter (DPF) Intake Temperature Sensor
5. Diesel Particulate Filter (DPF)
6. Diesel Particulate Filter (DPF) Differential Pressure Sensor
7. Diesel Particulate Filter (DPF) Outlet Temperature Sensor
8. Decomposition Tube
9. Diesel Exhaust Fluid (DEF) Tank - includes multiple components
10. Diesel Exhaust Fluid (DEF) Dosing Valve
11. Selective Catalytic Reduction (SCR) Catalyst - front and rear catalysts
12. Selective Catalytic Reduction (SCR) Intake Temperature Sensor
13. Ammonia Slip Catalyst (ASC)
14. Selective Catalytic Reduction (SCR) Outlet Temperature Sensor
15. Outlet NOx Sensor
** ECM and DEF Control Unit are not shown but are major contributors to aftertreatment
12
3
4
5
67
9
8
10
11
12
11 13
14
15
Exhaust Flow
Engine 59
Aftertreatment components are presented in the order of exhaust flow from the front of the after-treatment system to the end of the aftertreatment system. Mechanical components are pre-sented first, followed by control modules and sensors.
Diesel Oxidation Catalyst (DOC)
The DOC is the first element in the aftertreatment system. The DOC is a flow-through catalyst that uses hydrocarbons (unburned fuel) to create heat in the aftertreatment system. This heat is necessary for the DPF to oxidize soot and for chemical reactions to occur in the entire aftertreat-ment system.
The DOC cannot be cleaned or replaced individually; it is part of the entire DOC/DPF assembly.
Diesel Oxidation Catalyst (DOC)
60 Engine
Diesel Particulate Filter (DPF)
The DPF is located directly downstream of the DOC. The DPF is a wall-flow design that allows exhaust gas to pass through while collecting particulate matter (soot). When exhaust tempera-ture reaches at least 600°F (316°C), the soot begins to oxidize in the DPF.
The DPF cannot be removed and cleaned, and cannot be replaced individually; it is part of the entire DOC/DPF assembly.
Diesel Particulate Filter
Engine 61
Decomposition Tube
The decomposition tube is located downstream of the DPF and is considered the first part of the SCR system. The decomposition tube serves as the mounting point for the DEF dosing valve. Decomposition refers to the process of injecting DEF into the hot exhaust stream to produce chemical reactions that produce carbon dioxide and provide ammonia for the SCR catalysts.
Selective Catalytic Reduction (SCR) Catalyst
The SCR Catalyst is located downstream of the decomposition tube. The SCR catalyst is a two-part, flow-through catalyst that is effective at reducing NOx. When ammonia and NOx from the decomposition tube flow through the SCR catalyst, nitrogen (N2) and water vapor (H2O) are produced.
DecompositionTube
DEF DosingValve
SCR 1 SCR 2
62 Engine
Ammonia Slip Catalyst (ASC)
The ASC is located downstream of the second SCR catalyst. The ASC is a flow-through cata-lyst that removes any trace amounts of ammonia from the exhaust stream before the exhaust exits the aftertreatment system. This component may also be called the ammonia brick.
Engine Control Module (ECM)
The ECM is located in the back right corner of the engine compartment. The ECM controls all aspects of engine performance, including the operation of fuel, EGR, and aftertreatment compo-nents for reducing emissions.
ASC
ECM
Engine 63
Aftertreatment Sensors
The following information describes the locations and purposes of the sensors located along the aftertreatment system.
Intake NOx Sensor
The intake NOx sensor is the first sensor mounted on the aftertreatment tubing, just in front of the DOC. This sensor measures the quantity of NOx in the exhaust gas before it enters the after-treatment system. The intake NOx sensor includes a unique processor that is mounted externally from the sensor, and also includes a heater to bring the sensor to operating temperature quickly. The intake NOx sensor also detects the oxygen level in the exhaust.
The ECM compares the intake and outlet NOx sensor readings to determine the amount of NOx reduction that is achieved in the aftertreatment system, and to determine how much DEF to inject into the exhaust stream.
DOC Intake Temperature Sensor
The DOC intake temperature sensor is located just in front of the DOC. This sensor measures the temperature of exhaust gases after they leave the engine and before they enter the DOC. The ECM compares this temperature to the DPF intake temperature sensor to determine the temperature rise through the DOC. This sensor also helps determine the amount of fuel dosing for aftertreatment thermal management.
64 Engine
DPF Intake Temperature Sensor
The DPF intake temperature sensor is located between the DOC and the DPF. This sensor mea-sures exhaust gas temperature after it has passed through the DOC and also helps determine the amount of fuel dosing for aftertreatment thermal management.
DPF Differential Pressure Sensor
The DPF differential pressure sensor is a two-probe pressure sensor located before and after the DPF. This sensor measures the difference in exhaust gas pressure before the DPF and after the DPF. This measurement is used by the ECM to determine soot load in the DPF.
The two pressure sensor probes connect to an outboard sensor unit through heavy duty hoses.
DPFInlet Pressure Outlet Pressure
Sensor Unit
Engine 65
DPF Outlet Temperature Sensor
The DPF outlet temperature sensor is located downstream of the DPF. This sensor measures the temperature of exhaust gases after they have passed through the DPF and is used to monitor regeneration (soot oxidation) in the DPF. The DPF outlet temperature sensor is also used to measure exhaust temperature before it enters the decomposition tube and SCR catalyst.
The DOC intake temperature sensor, DPF intake temperature sensor, and DPF outlet temperature sensor all connect to one bracket-mounted sensor module on the side of the DPF.
SCR Intake Temperature Sensor
The SCR intake temperature sensor is located between the first and second SCR catalysts. This sensor measures exhaust gas temperature after the first SCR catalyst to help determine SCR efficiency.
DPF Outlet Temperature Sensor
Sensor Module
66 Engine
SCR Outlet Temperature Sensor
The SCR outlet temperature sensor is located at the end of the aftertreatment system, after the ASC. This temperature sensor measures the temperature of exhaust gases after all aftertreatment has occurred. The ECM uses this temperature measurement and other tempera-ture sensors throughout the aftertreatment system to determine if aftertreatment is effective.
Outlet NOx Sensor
The outlet NOx sensor is located at the back of the aftertreatment system, downstream of the ASC. The outlet NOx sensor measures the NOx quantity that remains after all aftertreatment has occurred. This sensor also includes a heater to bring the sensor up to operating temperature quickly. The ECM compares the inlet and outlet NOx sensor values to determine if the aftertreatment system is efficiently removing NOx. If NOx levels remain too high at the outlet NOx sensor, the ECM may command additional EGR or additional DEF dosing to lower these levels.
Engine 67
Diesel Exhaust Fluid (DEF) System
The EGR system is very effective at reducing NOx emissions in the engine, but current NOx emissions standards require additional measures to further reduce this pollutant. As a result, the Cummins 5.0L V8 Turbo Diesel engine uses a comprehensive DEF system in conjunction with a SCR system to reduce NOx levels.
NOTE: DEF may be referred to as “Reductant” in CONSULT-III plus.
Diesel Exhaust Fluid (DEF)
DEF is a non-toxic, non-flammable liquid that is injected into the exhaust stream to help convert NOx into harmless tailpipe emissions. DEF is composed of purified water and 32.5% urea. DEF is readily available from the pump at many fuel stations, or it can be obtained in containers. DEF is not harmful to handle, but it can be corrosive to certain metals.
DEF may be stored in sealed containers, away from direct sunlight, and in temperatures between 23 and 77° F (-5 and 25° C) for up to 18 months. However, for each 9° F (5° C) incre-ment in above this recommended temperature, shelf life is reduced by 6 months. In addition, DEF should not remain in the DEF tank of an unused vehicle for more than 6 months.
DEF has a freezing point of approximately 12° F (-11° C). Water should never be added to DEF. Adding water to DEF will change the DEF concentration, which will reduce SCR effectiveness. Chemicals introduced by adding unpurified water can also corrode or damage aftertreatment components or damage the DEF dosing valve. In addition, adding water to DEF will raise the freezing point.
DEF concentration can be tested using a refractometer that is calibrated for DEF.
Diesel Exhaust Fluid DEF Refractometer
68 Engine
DEF Tank
The DEF tank is mounted under the vehicle, behind the fuel tank. The DEF tank stores DEF that is used by the SCR system. DEF is added to the tank through a filler neck to the right of the diesel fuel filler neck. The DEF tank houses numerous components of the DEF system, including:
• DEF Control Unit
• DEF Pump Assembly
• DEF Fluid Line and Heater
• DEF Quality Sensor
DEFControl
DEF Pump Assembly
DEF Filler Cap
Unit
Engine 69
DEF Control Unit
The DEF control unit is mounted on the side of the DEF tank. The DEF control unit monitors DEF component readiness and communicates this status to the ECM.
DEF Quality Sensor
A DEF quality sensor is also mounted on the side of the DEF tank. This sensor detects the level of urea in the DEF to ensure the DEF concentration is acceptable for effective dosing (approxi-mately 32.5% urea). If the DEF quality sensor detects an incorrect DEF concentration, the DEF warning lamp in the combination meter will illuminate. In some cases, the MIL may also illumi-nate.
DEF Pump Assembly
The DEF pump assembly is mounted to the bottom of the DEF tank. The DEF pump is secured to the tank with a locking ring and O-ring seal. The DEF pump assembly includes the following components:
• DEF pump with non-replaceable filter
• DEF tank heater
• DEF level sensor
• DEF temperature sensor
• DEF pressure sensor
• DEF dosing line heater at inlet connection
DEF Quality Sensor
70 Engine
The DEF pump is commanded by the DEF control unit based on communication from the ECM. The DEF control unit monitors the DEF temperature, DEF pressure, and DEF level sensors to determine if the pump should operate.
When commanded to operate (dosing state), the DEF pump maintains pressure up to 90 psi in the DEF dosing line. DEF dosing will be covered in the upcoming topics in this section.
DEF Tank Heater
The DEF pump assembly includes a DEF tank heater to thaw frozen DEF in the tank. The DEF heater is a series of heated strips that are designed to evenly thaw frozen DEF in the tank. The DEF temperature sensor detects the temperature of the DEF and determines if tank heater oper-ation is necessary. The DEF pump will not prime until the DEF temperature has reached a suffi-cient temperature for dosing to occur. The DEF heater will activate and continue to heat the DEF based on the chart shown below.
DEF Temperature Sensor
The DEF temperature sensor is used as a key input for determining DEF heater and DEF pump operation.
DEF HeatingElements
Engine 71
DEF Level Sensor
The DEF level sensor reports the quantity of DEF in the DEF tank to the ECM. DEF level can be checked in the combination meter at any time.
DEF Pressure Sensor
The DEF pressure sensor monitors the pressure in the DEF dosing line to make sure adequate pressure is available for DEF dosing. The DEF pressure sensor also monitors the line pressure after engine shut down to ensure DEF has been purged from the line.
DEF Dosing Line Heater
A DEF dosing line heater is located at the end of the DEF dosing line where it meets the DEF pump. This heater is used to heat the dosing line between the DEF pump and the DEF dosing valve to prevent freezing.
72 Engine
DEF Dosing Valve
The DEF dosing valve is located on the decomposition tube. The DEF dosing valve is a PWM valve that injects a fine mist of DEF into the exhaust stream when commanded by the ECM. This injection of DEF is sometimes called SCR dosing because the SCR catalyst uses DEF to chem-ically convert NOx to nitrogen and water.
DEF Dosing Conditions
Certain conditions must be met for the DEF system to be active and ready to dose. Effective dosing requires the following:
• DEF tank level must be above 6% filled with DEF
• DEF quality must be verified
• The SCR intake and SCR outlet temperatures must be at least 392°F (200°C)
• Both NOx sensors must be turned on and reading NOx levels
• No active SCR system fault codes can be present
• DEF temperature must be above 27°F (-3°C)
Engine 73
DEF System States of Operation
After all preliminary conditions are met, the DEF system operates under three main states:
• Priming
• Dosing
• Purging
Priming State
When the SCR catalyst reaches approximately 392°F (200°C), the DEF control unit commands the DEF pump to start the priming process. The DEF pump draws DEF from the fluid tank, pressurizes the DEF, and then sends filtered DEF through the DEF dosing line to DEF dosing valve. The ECM commands the DEF dosing valve to open and close to purge any air from the system. After the system builds sufficient pressure, the DEF dosing system is ready to dose.
74 Engine
Dosing State
The DEF pump runs continuously to maintain DEF dosing line pressure when the system is in the dosing state. The pump runs whether or not the dosing valve is spraying DEF. When the ECM determines that DEF dosing should occur, it sends a PWM signal to energize the DEF dosing valve. The DEF dosing valve opens and pressurized DEF is injected into the decomposition tube.
Purging State
When the engine is turned off, the DEF system enters the purging stage to prevent DEF from being left in the system, and in cold climates, potentially freezing. An audible click and pumping sound is heard from the diesel exhaust fluid dosing unit when it is in a purge cycle. The DEF pump will slide its internal reverting valve and cause a change in the flow direction of the DEF. The DEF pump pulls all of the DEF out of the DEF dosing valve and DEF dosing line, and then returns the unused DEF to the fluid tank. During the purging process, the DEF dosing valve opens, eliminating any vacuum created in the line for a more complete purge process.
DEF Inducements
The vehicle must operate with DEF present in the system. DEF is required to meet strict NOx emissions requirements. If the ECM detects the absence of DEF, it will provide warnings to the operator in the combination meter until sufficient quantities of DEF are added. If the vehicle is driven without DEF, inducements (engine power reduction) will occur in several stages based on the distance driven without DEF.
Engine 75
DEF Warning Messages
The combination meter begins to display warnings when the DEF level drops to 25%. If mes-sages are ignored, vehicle speed will eventually be limited to 5 mph.
• DEF Low, XX% Refill Soon - displays when DEF level reads 15-25%
- DEF Lamp State: Solid
• DEF Low XX%, Limited Engine Power Soon - displays when DEF level reads 5-10%
- DEF Lamp State: Flashing
• DEF Low, Limited Engine Power in XX Miles - displays when DEF driving range is between 0-249 miles (below 5%) - engine torque is reduced
- DEF Lamp State: Flashing
76 Engine
• DEF Empty, 5 mph Limit Soon, Refill DEF - engine torque will be reduced. Speed will be lim-ited to 5 mph when any of the following occur:
- Engine shutdown and restart
- Engine is idled for an extended period of time (approximately 1 hour)
- Control module detects fuel level in the tank has increased
- DEF Lamp State: Flashing
• Speed Limited to 5 mph, Refill DEF - vehicle speed is limited to 5 mph
- DEF Lamp State: Flashing
In addition to DEF level warnings, DEF system error messages may also be displayed when DEF dosing system errors are detected. These warnings are accompanied by similar engine derate strategies.
1
2
3
4
Engine 77
Aftertreatment System Operation
The aftertreatment system relies on the heat created by the combustion process to begin per-forming the chemical conversion of harmful emissions into harmless emissions. The aftertreat-ment system is designed to primarily reduce soot and NOx emissions before they exit the tailpipe.
Soot Oxidation
The aftertreatment system contributes to emissions control when exhaust gas temperatures reach normal operating temperatures. The ECM uses several methods to raise the temperature of the DOC quickly so soot can begin to oxidize in the DPF, and so sufficient heat is available for the SCR system.
The ECM may limit EGR cooling or may use the rotary turbine control valve to provide exhaust throttle to quickly raise exhaust gas temperatures. The ECM monitors the DOC intake tempera-ture sensor and DPF temperature sensors to determine when temperatures are high enough for the DOC to be effective for aftertreatment.
Soot begins to oxidize in the DPF when exhaust gas temperatures reach approximately 600°F (316°C). Soot oxidation is the process of chemically converting particulate matter into a gas form. This process is also known as DPF regeneration.
Passive Regeneration
When the Titan XD is driven under conditions where exhaust temperatures can reach normal operating temperatures, like long highway cruising, towing heavy loads, etc., soot may be oxidized without additional help from the engine. This method of DPF regeneration is called pas-sive regeneration. Passive regeneration occurs when exhaust gas temperatures reach approxi-mately 600°F (316°C).
78 Engine
Active Regeneration
If the vehicle is consistently driven at low speeds, under low duty cycle operation, or in other conditions where the exhaust does not reach high enough temperatures, passive regeneration of the DPF may not occur. Under these circumstances, active regeneration may be required.
The ECM monitors the soot load in the DPF by monitoring the DPF differential pressure sensor. If the DPF differential pressure sensor indicates that the soot load is too high, the ECM will take measures to increase the temperature in the exhaust system in an attempt to oxidize the soot.
The ECM may begin to close the EGR valve and open the EGR bypass valve to prevent EGR from being cooled. This helps raise the temperature of the exhaust. If additional heat is needed in the exhaust system, the ECM will command extra fuel injections into the cylinders during the exhaust stroke. These extra fuel injections result in unburned fuel being delivered to the DOC in the form of hydrocarbons. Hydrocarbons react with the DOC and the resulting chemical reac-tions produce additional heat in the aftertreatment system to begin oxidizing soot in the DPF.
Engine 79
Stationary Regeneration
Over time, the soot level in the DPF may become high enough that a warning is displayed in the combination meter. If increased duty cycle driving and active regeneration cannot oxidize the soot in the DPF, a stationary regeneration may be required.
Stationary regeneration can only be performed by a technician using an Active Test in CONSULT-III plus. This procedure must be performed outdoors and away from flammable objects. When a stationary regeneration is initiated, the procedure gradually raises exhaust gas temperatures to extremely high levels in an attempt to oxidize soot in the DPF. During a station-ary regeneration, exhaust gas temperatures can exceed 1,100°F (593°C). Always read and fol-low all setup instructions and precautions in CONSULT before initiating a stationary regeneration.
In some situations, CONSULT will not allow a stationary regeneration. Certain active DTCs may cause CONSULT to deny this procedure to protect vehicle components from damage.
80 Engine
SCR Operation
The SCR system operates when exhaust temperatures have reached a certain threshold and the DEF system has entered the dosing state. The intake NOx sensor must be heated to 300°F (149°C) and the outlet NOx sensor must be heated to 400°F (204°C) to begin measuring NOx levels in the exhaust. When SCR catalyst temperatures reach approximately 392°F (200°C), DEF may be injected (dosed) by the DEF dosing valve into the decomposition tube. The amount of DEF injected into the exhaust stream is directly proportional to the amount of NOx detected by the NOx sensors.
A small quantity of DEF from the DEF tank is injected by the DEF dosing valve into the decom-position tube. A chemical reaction between the exhaust and DEF occurs as the chemicals travel in the decomposition tube, creating ammonia vapor. The ammonia vapor reacts with the NOx in the SCR catalyst, breaking the exhaust down into nitrogen and water vapor. The ASC breaks down any trace amounts of ammonia in the exhaust before it exits the aftertreatment system.
Engine 81
Glow Plug System
The Cummins 5.0L V8 Turbo Diesel engine uses a glow plug system to assist in engine starting during cold weather conditions.
Glow Plugs
Glow plugs are threaded into the tops of the cylinder heads above each of the eight cylinders. A tapered area on the lower portion of the glow plug mates with the taper in the cylinder head to seal the glow plug opening. When energized by the Glow Plug Control Module, the glow plugs can reach temperatures over 1,500° F within two seconds. This extra heat within the cylinder helps promote combustion of fuel when ambient temperatures are low.
82 Engine
Unlike fuel injectors, glow plugs do not use O-rings or washers to seal the glow plug in the cylinder head. Instead, the glow plugs rely on a tapered seat that mates with a taper in the cylinder head. If the tapered seat on the glow plug is damaged, the glow plug may not seal properly, leading to combustion leaks. In addition, the glow plugs are grounded through the thread and seat area. Do not apply anti-seize to the threads or seating surface or the plug may not be grounded properly.
Glow plugs are fragile and should be handled with care when removing or installing. Never remove or install a glow plug with an impact wrench. When removing a glow plug with a deep well socket, make sure the socket is inserted straight to avoid contact with the upper glow plug tip and to avoid bending the glow plug body. The intake manifold or stage 2 fuel filter housing must be removed to access most glow plugs and avoid bending the plug. When installing a glow plug, finger tighten the plug first and then tighten the plug to specification with a torque wrench. Finally, do not use starting aids on the Cummins 5.0L V8 Turbo Diesel engine as this may cause severe engine damage.
Tapered Seat
ThreadEngagementArea
Engine 83
Glow Plug Control Module
The glow plug control system is controlled by the ECM and the Glow Plug Control Module. The Glow Plug Control Module is located in the back left corner of the engine compartment to the left of the brake booster.
The Glow Plug Control Module receives fused power directly from the batteries. The ECM communicates with the Glow Plug Control Module over the CAN. The glow plugs are grounded through the cylinder head. The ECM calculates an average temperature based on inputs from the engine coolant temperature sensor, the air intake manifold temperature sensor, and an inter-nal temperature sensor in the Glow Plug Control Module. After the required conditions are met, the Glow Plug Control Module sends an output to each of the eight glow plugs individually. The Glow Plug Control Module monitors the operation of individual glow plugs and reports failures back to the ECM. Glow plugs begin activating at key ON during the wait-to-start sequence, and will continue to operate after cranking if the ECM determines the glow plugs are needed.
84 Engine
Engine Oil
The standard engine oil requirement for the Cummins 5.0L V8 Turbo Diesel engine is 10W-30 oil that meets CJ-4 specifications for diesel engines. This type of engine oil has low-ash qualities for use in diesel engines that use an exhaust aftertreatment system. 5W-40 engine oil that meets CJ-4 specifications may be used in arctic climates.
NOTE: The factory oil fill may include colored dye for manufacturing leak tests.
Engine Oil Life Monitor
The Titan XD is equipped with an engine oil life monitor system. This system provides oil life messages in the combination meter.
• Oil Control System - XX Miles
- Message displays the remaining miles until an engine oil and filter change is required.
- The oil and filter change interval is reduced when the vehicle is driven on a severe duty cycle, such as towing.
• Engine Oil - Service Due Now
- Message displays when the engine oil and filter should be changed.
Engine 85
TRANSMISSION & DRIVELINE
Aisin 6-speed Automatic Transmission
The Titan XD uses an Aisin automatic transmission with six forward gear ranges and reverse. This transmission is based on the same design as the transmission used in many 3500 and 4500 series trucks. This transmission includes the following features:
• High torque capacity to compliment the Cummins 5.0L Turbo Diesel engine
• Tow/Haul mode selector and manual shift buttons on the column-mounted gear selector lever
• Transmission fluid cooler on all models
• Nissan Matic-K fluid is used in this application
• Transmission Control Module (TCM) located in front passenger foot well area
86 Transmission & Driveline
Transmission Diagnosis and Service
At vehicle launch, serviceable items on the Aisin transmission will be limited. Some of these ser-viceable items include the TCM, valve body assembly, torque converter, and rear oil seal. Special tools are available to adjust or verify the adjustment of the Park/Neutral position switch, and to install the real oil seal. If the transmission must be removed for service, be sure to support the transmission properly to avoid damaging the transmission fluid pan.
If the transmission or TCM is replaced, the TCM must be programmed using CONSULT.
TCM
TCM
Transmission & Driveline 87
Transmission Work Support Quick Learn (Transmission Adjustment)
If the transmission or the TCM is replaced, a CONSULT Work Support procedure must be used to help calibrate the TCM to the IP characteristics of the transmission. Each transmission sole-noid’s current/pressure characteristics may vary slightly from transmission to transmission. The TCM must learn these individual characteristics. This procedure adjusts for any differences to ensure the correct pressures are learned for optimum shift quality and timing.
Transmission Fail Safe
If TCM communication is lost, or a DTC is set that prevents accurate shift scheduling, the trans-mission may enter a fail safe mode (limp-in). Fail safe mode attempts to prevent or limit damage to the transmission by limiting the available gear ranges. Fail safe is as follows:
• The transmission will only operate in 3rd gear and Reverse
• If vehicle speed is above the range for 3rd gear when fail safe is initiated, 5th gear will be available until the vehicle reaches a safe speed to allow 3rd gear
• When the transmission shifts to 3rd gear, 5th gear is no longer available
• The transmission continues to operate only in 3rd gear and Reverse until the condition has been addressed
88 Transmission & Driveline
Transfer Case
The Titan XD may be equipped with an electronically controlled transfer case. A drive mode selector switch is located on the instrument panel and can be used to select 2WD, 4H, or 4LO. When the switch is used to select a drive mode, an electric motor on the transfer case engages the correct gears in the transfer case. Gear position is monitored by a position switch and is dis-played in the combination meter.
ElectricMotor
PositionSensor
Transmission & Driveline 89
Front and Rear Axles
The front and rear axle/differential assemblies are purpose built for the Titan XD by American Axle Manufacturing. The front axle is a 9.5-inch unit and the rear axle is a 10.5-inch unit with an available electronic locking differential on PRO-4X models. These axles are designed to support the towing and hauling capabilities of the Cummins 5.0L Turbo Diesel engine.
90 Transmission & Driveline
SUSPENSION
Front and Rear Suspension
Titan XD uses a double wishbone front suspension with a solid steel stabilizer bar. The rear sus-pension is a solid axle design with leaf springs. Twin tube shock absorbers are standard while Bilstein mono tube shocks are used on PRO-4X models.
Suspension 91
Wheels and Tires
Several wheel and tire combinations are available:
• 17-inch aluminum alloy wheels with LT245/75R17 tires
• 18-inch aluminum alloy wheels with LT275/65R18 tires
• 20-inch aluminum alloy wheels with LT265/60R20 tires
A four-corner Tire Pressure Monitor System (TPMS) is standard on all models. Tire pressures front and rear are different depending on the tire/wheel combination.
92 Suspension
BRAKES
Standard Brake System Features
The Titan XD has standard front and rear disc brakes.
• Front: 14.2 x 1.5-inch ventilated discs with twin calipers per corner
• Rear: 14.4 x 1.2-inch ventilated discs with twin calipers per corner
Standard electronic braking system features include:
• ABS with Vehicle Dynamic Control (VDC) and Traction Control System (TCS) functions
• Electronic Brake Force Distribution (EBD)
• Hill Start Assist
Rear BrakesFront Brakes
Brakes 93
ABS Actuator and Control Unit
The electronic brake control system on the Titan XD is very similar to the system used on the Nissan NV. The control unit is integrated with the actuator and motor/accumulator assembly and controls the ABS, VDC, TCS and EBD functions. The actuator includes an accumulator, motor, pump, and a series of Cut Valves and Suction Valves that control hydraulic brake fluid delivery.
Trailer Braking
The Titan XD can be equipped with a number of features and components that can assist in towing a trailer. Some of these available functions are electronically controlled:
• Trailer Sway Control - uses the braking system to stabilize a trailer if it begins to sway
• Hill Descent Control - uses the transmission and braking system to help stabilize vehicle speed while descending steep grades
• Trailer Brake Controller - fully-adjustable integrated controller on the instrument panel that is used to apply the trailer brakes
• Trailer Light Check - displays the status of trailer lights in the combination meter, allowing one-person light checks
Accumulator
Brake Fluid Reservoir
ABS Actuator and Control Unit
94 Brakes
Integrated Trailer Brake Controller
A trailer brake controller is available on the Titan XD. This electronic controller is located on the center stack of the instrument panel and controls the output circuits for the rear tailer wiring. The system is compatible with electric-actuated and electric-over-hydraulic trailer brakes with up to four axles.
The trailer brake controller can operate in two modes:
• Automatic: Normal operating mode that uses the operator’s settings to automatically apply the trailer brakes when the vehicle brake pedal is depressed
• Manual: Initiated by adjusting the manual control lever from the default position. This pro-vides output to the trailer brakes without applying the vehicle brake pedal
Gain -Gain +
Boost
LED Display
Manual Override
Brakes 95
Trailer Brake Controls
The trailer brake controls include:
• Gain: Plus and minus buttons are used to increase or decrease braking force to the trailer brakes (range of 0-10)
• Boost: Used to adjust the feel of the automatic braking event when the vehicle brake pedal is depressed (range of 0-3)
• Manual Override: Pinch lever used to apply the trailer brakes without applying the vehicle brake pedal
- The amount of brake output voltage is proportional to the amount of pinch travel
96 Brakes
STEERING
Steering System
Titan XD uses a hydraulically-assisted, recirculating ball steering system with a parallel rod steering linkage. An air-to-oil power steering fluid cooler is located behind the front grille.
Recirculating Ball Steering System
Power Steering Fluid Cooler
Steering 97
HEATING, VENTILATION, AND COOLING
PTC Heater
When engine coolant temperatures are low, heating the cabin can be difficult. For this reason, the Titan XD uses a PTC heater within the HVAC ducting to provide supplemental cabin heat. Air from the blower motor passes through the PTC heating grid and is heated before exiting the HVAC vents. The PTC heater can be removed by disconnecting the electrical connector and removing two screws.
98 Heating, Ventilation, and Cooling
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100 Heating, Ventilation, and Cooling
