-Ray Grooms

Homemade Strap

Wrench Here is an easy solution to a frequent shop need, an adjust-

able strap wrench. Steel chains

can do too much damage and nylon straps do not have enough

friction. So, cut 5/16" slots in a

medium sized socket , 5/8 to

7/8, and slip a rubber belt into

the slot. A ratchet can now be used for turning force. Timing

belts and serpentine belts can be

used for small to large applica-

tions.

Testing for Parasitic

Drain Across Fuses

To expand upon a previous Tech

Tips article, I would like to

point you in the direction of 4

different conversion charts. These charts allow for you to

perform parasitic drain testing

across different fuse types with your meter set to the millivolt

setting. The mv reading can be

converted to ma using the charts provided here; http://

info.powerprobe.com/

fusecharts, or visit the Y-Drive.

VAT 40 Accuracy?

The VAT-40 is a well-trusted

machine which has been used by many for a long, long time.

While this machine is great for

load tests be warned that the amperage measurement may be

inaccurate. The picture below

shows a VAT-40 readout of near 100a, while a Fluke amp clamp

connected at the same point dis-

plays 81.9a. A 15-20% margin

of error exists on this VAT-40.

Tech TipsTech Tips A Tri-annual

Publication

GM Fleet Issue!

With our shop hav-

ing recent ly be-

come a GM Flee t,

we have decided to

dedica te much of

this issue to cover-

ing the var ious as-

pects of what be-

ing a GM Flee t is

all about , to the

technician. Read

on to f ind out

more!

The Tech Tips Team

Eric Irwin

Ray Grooms

Sal Guerrero

Cover Story: Fleet Services Becomes a GM Fleet!

Many thanks to our manage-

ment staff and

Eric Irwin who helped to estab-

lish the City of

Oxnard Fleet Ser-

vices Division as an official GM Fleet. So what is a GM Fleet?

GM Fleet equals access to informa-

tion power; it provides our shop with the same information available to GM dealer

technicians. Included in the benefits of being

a GM Fleet are GM’s Service Information

system, the GM Vehicle Inquiry System, TechLink, and access to GM Service Techni-

cal College.

Service Information (SI) is perhaps the most useful resource as it provides direct

access to repair manuals, campaigns, bulle-

tins, wiring diagrams, and all GM service literature. To access SI you will need to

setup a temporary ID though GM using our

Fleet Account Number (FAN). If you have-

n’t already done so, get in touch with me for further assistance. Additionally, SI requires a

login and password change every 30 days,

and if you have not logged in for 60 days your username will be purged from the sys-

tem.

Another great benefit of being a GM Fleet is GM’s Service Technical College

(GMSTC). The training site provides free

access to online based courses, some video

on demand courses, and the possibility of enrollment in GM hands-on courses. Come

see me to see about setting up an account.

The GM Vehicle Inquiry System (GMVIS) allows for account holders to pull

dealer repair records according to VIN. A

very useful tool for checking status of cam-paigns and repairs performed.

Lastly, there is TechLink, a monthly

GM publication offering technical tips and

tricks, and information as related to GM ve-hicles. Past issues of TechLink can be

downloaded in PDF format. Visit

www.gmfleet.com/fleet-tools.html to ex-plore the benefits mentioned above and

more!

In This Issue

Cover Story: GM Fleet P.1

Tools & Equipment: Tech2Win P.1

Electronics Corner: Pull-Ups & Downs P.2

Case Study Special: SEMA P.2

Industry News: Photosynthesis as a Fuel P.3

Auto 101: GM Service Training P.3

Tech Tips P.4

Scope It! Compression Waveforms P.4

Issue 2 December, 2013

V o l u m e 3

One of the benefits of being a GM Fleet is the potential access to factory tooling, which brings us to the windows based version of GM’s Tech 2, the

Tech2Win. The Tech2Win is a software based diagnostic tool

that provides factory level diagnostics and reprogramming

through the GM MDI, or an authorized J2534 device, which works in conjunction with GM’s Technical Information Sys-

tems (TIS2). The Drewtech CarDAQ-M has recently been

authorized as a J2534 pass through for the Tech2Win, mean-ing our shop could potentially acquire this tooling at a re-

duced cost as we already have the CarDAQ-M.

Tools & Equipment; GM’s Tech2Win

“By the Techs, For the Techs”

Scope It! Compression Waveforms

Technician Tips

-Eric Irwin

The Pico WPS 500 is a powerful pressure transducer kit that al-lows for pressure measurements up to 500 psi to be displayed as a wave-

form. This is especially useful for compression waveforms which are a key in determining the proper mechanical operation of a cylinder. When meas-

uring compression with the WPS 500, also known as an In-cylinder pres-sure transducer, there are 2 basic test to perform, cranking and running

compression tests. In this Scope It! overview we will focus on the basics of running compression at idle.

Scope Settings; The WPS hardware must be powered by usb, calibrated, and have a range selected. Look on the back of the WPS for the 3 ranges

available. If you’re using the Autonerdz branded version of Pico you will find custom WPS probes installed… use these as they have been refined

for better operation. When performing running compression checks you will typically see around 70psi, anything below 40psi is definitely a prob-

lem. Set the probe range to the –25 / 100psi scale and your time base to 50ms per division. I would suggest using a repeat trigger on the compres-

sion tower to stabilize the image. The waveform to the left shows 720o of crank rotation and 360o

of cam rotation, a full 4-stroke cycle. The compression tower should be symmetrical on both sides and the expansion pocket should dip fall to the

same level as the intake level. The exhaust valve should open about 30o before point A, which is the beginning of the exhaust ramp / plateau. This

plateau runs from point A to B at which time cylinder pressure is equalized with exhaust pressure (near 0). The peak exhaust plateau pressure should

be very close to the BDC mark. Valve overlap occurs between points B and C, the exhaust valve closes at point C and cylinder

pressure is drawn into a vacuum during the intake stroke. The cylinder is then sealed and compression occurs. There is a lot of

information contained in this type of waveform, but in general you would want to see consistency across the cylinders in regards

to the compression tower and valve events. Bank to bank com-parisons can be made to assess timing of valve events. There are

also some great 3rd party software applications that allow for image overlaying where the degree indicators are written in and a

database of valve timing events can be added to assist in diagno-sis. A good case study using pressure transducers was done by

Motor Magazine. You can also read this on the Y-Drive in the

Tech Tips folder. ATS has published some great information about this subject, and various users of the Autonerdz Forums

have contributed tons in this regard as well. -Er ic Irwin

-Sal Guerrero

Need more Tips? Look no

further, http://

sandyblogs.com/techlink/.

TechLink provides a monthly

newsletter which contains all

types of useful GM informa-

tion, and it is free to access,

no account needed… any-

body can access it.

-Ray Grooms

4 1

-Eric Irwin

Announcement!

Fleet Services welcomes Fer-

nando Hernandez to the 2-PM

crew.

72psi Compression

peak, True

TDC

Expansion

pocket

Compression

Tower

Exhaust

Plateau

A

-11 psi

0 psi

720o / 360o Crank / Cam

rotation, 1 4-stroke cycle.

Power, Exhaust, Intake ,

Compression

B C

D

0o

540o 360o 180o

720o

Power Exhaust Intake Compression

T

D

C

T

D

C

B

D

C

B

D

C

T

D

C

~100a

81.9a

DRAGG (Drag Racing Against Gangs & Graffiti) recently came to ask for our assis-

tance in adding a police package onto a brand new 2013 Ford Focus ST. Under the support

and direction of Bill Birch and Joe Rodriguez, a small band of fleet technicians came to-

gether to meet the challenge in front of them; assist DRAGG in building a SEMA quality

vehicle worthy of Ford’s

main stage.

The efforts of Fleet

Services, local shops, and

the youth that participate

in the DRAGG program

were collectively recog-

nized with a Ford Prod-

uct Excellence award at

the 2013 SEMA show in Las Vegas. The vehicle comes stock with 252hp but is estimated

to be in the 280hp ballpark after modifications to the stock turbocharger and exhaust sys-

tems were done by Vortech and Borla.

Also installed on this vehicle are; A Ford Racing air scoop, short throw shifter kit ,and

K&N cold air intake, an Eibach suspension kit, Wilwood brake kit, Motegi rims, and

wheel spacers. With a DRAGG / Ford paint design (painted by Commercial Auto Body),

decals by Ron's Signs,

and pin striping by J&N,

the vehicle really comes

to life. Body modifica-

tions include a Rally In-

novations splitter kit and

a custom rear spoiler

wing. A Rally Innova-

tions Quick Trac Harness Bar compliments the Cobra racing seats which were custom

modified to fit by Weldon Hot Rods Inc.

In the fleet realm of modifications there were extensive add-ons equipped to this vehi-

cle. All parts were provided by DRAGG and include; A 55a AC to DC power converter to

allow the package to run independently of the battery, a remote mounted 2-way radio sys-

tem w/ a

Sti-Co

Under-

cover

antenna,

a one of-

a-kind

custom

pushbar, gun rack, and lighting package which include a total of 22 peripheral LED’s and a

Federal Signal Legend lightbar. A 200w dual siren system with a 100w option provides

plenty of noise (along with a Kicker Audio system) and a custom pic microcontroller lcd

interface adds a unique touch to the vehicle allowing for it to interface with the police

package. The vehicle did very well at the SEMA show and has since received national at-

tention, potentially elevating the DRAGG non-

profit organization to it’s next level of evolu-

tion. The final outcome of the vehicle has met

and exceeded expectations and Fleet Services

is proud to have been part of that process. Visit

the DRAGG website to find out more! http://

www.draggteam.com/

Modern control modules work digitally meaning that input signals are either high or low, or on and off. A third logic input state is “floating”, which is when a signal is

neither high nor low, and undesirable in logic level circuits. The job of a pull up or pull down resistor is to provide a clean signal to the control-ler and to ensure that the high / low conditions are met (not floating). They ensure that expected voltage levels are reached in order for deci-

sions to be made by a controller. While this may not seem too impor-tant to the average technician, it can play a pivotal role in knowing what to expect during electrical system analysis. The picture to the left de-

picts a pull-down

resistor. R1 (resistor 1) is tied to ground, so when the switch is open the controller sees a ground, or logic level low / near 0v. When the switch is closed a

voltage , Vcc (IC power supply), is applied to the controller input (MCU) and the resistor. The re-sistor acts as a small load, in this

example a 5v signal applied to a 4.7K resistor would flow 1ma

of current. The circuit results in a high or low voltage. Have you ever noticed that a Brake Pedal Position switch is

grounded when open and hot when closed? This is a pull down resistor at work The ECM needs a high or low signal to make a logic level decision. In an ADC sensor circuit, such as a TPS which typically sends an ana-logue signal of .5v to 4.5v, the pull-down resistor is necessary for open

and short detection. If the signal wire is open, the controller sees 0v due to the pull-down, if it is shorted to power it will see 5v. Visit the GM training website at https://www.centerlearning.com/HomePage/Portal.asp and take the Electronics courses under the Fundamentals training path to learn more! See Ray

if you have not yet created an ac-count.

Case Study Special: A SEMA Car in the Making The Electronics Corner: Pull-Up &

Pull-Down Resistors

-Eric Irwin

A viable source for an alternative fuel has been a hot topic for over a decade

now. Fossil fuels are said to be in short

supply and contribute to global warming

and pollution. Coal is abundant but harm-ful, wind power and bio-fuel from corn

take up too much land, and current solar

power energy is too costly and inefficient. Hydrogen has been discussed as the alter-

native fuel solution but concerns over cost,

safety, and needed technological advance-ments have hindered its progress. But re-

cent developments in artificial photosyn-

thesis are promising and may pave the way

to the future of alternative fuels. The goal of artificial photosynthe-

sis is to split water molecules into hydro-

gen and oxygen, providing for a cheap and abundant fuel source. This is done in the

same manner that a leaf converts light en-

ergy into chemical

energy, but on a much

more massive scale. While a forest full of

leaves would only pro-

vide a small amount of power, an artificial

photosynthesis machine that could be 15 -

25% efficient would be more than twice as efficient as current methods of generating

fuels. Researchers at the University of

Stanford have recently found a way to

make solar photovoltaic material more resilient which may make this a reality.

The director of the University of

North Carolina’s Energy Frontier Re-search Center in Solar Fuels, Thomas

Meyer, has found a single catalyst for arti-

ficial photosynthesis that could produce a liquid or gaseous fuel from solar energy.

This fuel can be used for transportation

purposes or electrical power generation.

Furthermore, artificial photosynthesis has the potential to produce more than 1 type

of fuel; hydrogen, methane, and methanol

are amongst the possible fuels to be pro-duced.

Organizations like JCAP, the na-

tions largest research team dedicated to the development of solar fuel generating tech-

nologies, along with others, lead the way

into the future of alternative fuels. Al-

though the advances are not far enough along to put this technology into produc-

tion, scientists are close. The promise of a

clean burning fuel with no harmful by-products seems to be around the corner.

Industry News: Artificial Photosynthesis as a Fuel Alternative

-Sal Guerrero

Auto 101: Air Fuel Ratio Sensors

-Eric Irwin

The AFR Sensor (sometimes called the Wide-Band O2 sen-sor) is nothing new and has been on cars since at least the early 2000’s.

More recently however these are becoming the industry standard and while they may not be on every model they are becoming the dominant

type of oxygen sensor. The AF sensor is essentially 2 oxygen sensors built into 1 which act as an Oxygen ion pump. 1 sensor acts as a signal

cell, and the other as a pump cell. The Bosch AFR sensor is capable of measuring AF ratios between 9:1 and up to free air, whereas the con-

ventional O2 sensor was somewhere between 12:1 to 16:1. Because the AFR sensor is a complicated sensor it is more beneficial to discuss

what can be observed and tested, rather than the theory of operation. Having mentioned that the AFR sensor is an ion pump, the

means to controlling the air-fuel ratio is done through the pumping of current which is controlled by the ECM. What we need to understand

here is that the AFR voltage PID that is available via a scanner is a conversion of the control current. The current that is pumped is in the

milli - micro amp range and cannot accurately be measured with con-ventional tooling. Because of this the scan tool becomes an essential

tool for AFR sensor diagnosis. The normal range of this parameter is around 3 to 3.6v, which varies by manufacturer. In the EASE capture above, an AFR sensor voltage of 3.3v represents a 14.7:1 air-fuel ratio, which is also known as LAMBDA where a value of 1.00 = 14.7:1 (stoichiometric). Under

1.00 = Rich, and over 1.00 = Lean. In the EASE capture above I performed enrichment and enleanment testing to see how the AFR sensor would re-spond, and what I found is that AFR sensor operation can be verified in much the same way that a standard zirconia O2 sensor is verified. It is important

to notice that the control current pumps in both directions, positive and negative. The goal of the AFR sensor is to maintain a 1.00 LAMBDA value, when a rich condition is detected the control current responds by going negative, when a lean condition is present it responds by going positive. On this

vehicle both the control current and converted voltage PIDS are given, note that they respond to AF changes in the same manner. Fuel trims also respond accordingly. So testing really isn’t that much different than what it was before… with this information at hand we should feel comfortable in verifying

the normal operation of these sensors. As a side note, the K110 MicroProbe is capable of measuring amperage on these.

3

-Eric Irwin

2

A work in Progress

Finished

Product

Stock

Vehicle

Add-on Equipment

Control Panel

LCD Interface and Smart

Siren Controller Harness Bar &

Gun Rack

Cobra Seats

Pull-down

Ct.

Pull-up Ct.