phaser tech on chevys

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November 2001

Volume 3, No. 1

A monthly publication for GM Dealership Service Professionals

Service Operation

Contents

Cam Phasing Technology . . . . . . . . . . . . . . . . .

Techline News

Benefits of a Pentium 4 Processor . . . . . . .

PC Viruses Are Still a Concern . . . . . . . . . .

Class 2 Tip of the Month . . . . . . . . . . . . . . . . .2

Power Modes . . . . . . . . . . . . . . . . . . . . . . . .4

EVAP System Tester . . . . . . . . . . . . . . . . . . . .6

GM Oil Life System Revisited . . . . . . . . . . . . . .

Tech Tips

Clunk During a Turning Maneuver . . . . . . . . .7

Radio Audio Output Too Low . . . . . . . . . . . .8

Bulletins . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Techline News

operating systems in the future. Withthe proper software, security featurescan be increased greatly over previousPCs.

Another great benefit of a Pentium 4is the price of a business grade PC. Theprice will actually be less than that of aPentium III with equivalentspecifications. A PC with a Pentium 4processor will ensure the greatestperformance now and also allowflexibility for the future.

TIP: Pentium 4 processors presentlyexhibit a conflict with the SI 2000software. However, this can becorrected with certain modification. JRE1.3.1 must be downloaded fromhttp://java.sun.com before loading SI2000. Once SI 2000 is loaded, only theBasic version will function; the Enhancedwill not work. This will be corrected in afuture release of SI 2000.

– Thanks to Sam Hutson

2002 4.2L RPO LL8

(VIN S)

Why Cam Phasing is Used

As emissions standards continue to growstricter, devices have been added tovehicles to decrease pollutants. These haveincluded AIR , PCV and EGR. Recentlyengineers have sought ways to control

major pollutants through engine design,while increasing torque and horsepower.Cam phasing is one of the newtechnologies that provides a finer control ofengine operation.

At engine combustion chambertemperatures above 2500°F, nitrogen mixeswith oxygen to form oxides of nitrogen(NOx) which is a major contributor to smog.Because each cylinder experiencescombustion temperatures well above thatlevel, methods for reducing combustiontemperatures have been a goal for allautomotive manufacturers.

Traditionally the method forreducing the formation of NOx isthrough the use of an externalexhaust gas recirculation (EGR)valve. Exhaust gas isreintroduced into the intakemanifold through a valve,diluting the intake charge andeffectively reducing combustionchamber temperatures and the

formation of NOx. A side effectof introducing external EGR toreduce NOx is that it causes thehydrocarbon (HC) levels to increase.

A more effective method of controllingemissions is to increase intake and exhaustvalve overlap. Valve overlap refers to theamount of time in the four-cycle engineevent when both the intake and exhaustvalves are open. A reversion occurs in thecylinder as the piston is moving down whileboth valves are open. Exhaust gas is drawnback into the cylinder, simulating an EGRfunction. Being able to control the length of

Cam Phasing Technology

continued on page 2

Pentium 4 processors have recentlybeen added to the Techline HardwareSpecification (http://service.gm.com).When evaluating a new PC for theService Department, one may wonderabout the benefits of a Pentium 4 overanother processor.

Increased system responsiveness formultitasking means that moreapplications can simultaneously be openwith less chance of the PC locking up orslowing down.

This Pentium 4 chipset was designedfor enhanced web based performance.As more Service Departments use theWorld Wide Web and other applicationsbecome web based, a Pentium 4processor will enhance the performanceof these applications.

The Pentium 4 design is based on theIntel® NetBurst™ technology. This newarchitecture promotes top-levelperformance by the PC and will promotegrowth for both new applications and

this event can substantially lower NOx. Hlevels are also reduced by re-burning the of the exhaust event which is rich inhydrocarbons. However, placing thecamshafts in a permanent increased overposition would affect idle and low rpmperformance. The greater the overlap, thelower the intake manifold vacuum levels.

A cam phaser allows the position of th

Benefits Of A Pentium 4 Processor

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http://java.sun.com/





Techline News continued from page 1

Last April, we brought you an articleabout protecting your dealership’scomputers from viruses. (Back issuesavailable on the TechLink web page, athttp://service.gm.com.) As you’ve nodoubt heard in the news, viruses

continue to be a problem, and thelikelihood is high that your system willcome under attack.

Due to the recent impacts of theCodeRed and Nimda viruses,maintaining virus protection onTechline clients has never been moreimportant. In order to assure maximumsecurity, anti-virus software should beinstalled and maintained on all Techlineclients.

There are currently over 57,000known viruses, and new viruses arefound all the time, so updating anti-

virus definition files on a weekly basisis a necessity. Once a virus infects aclient PC, it may spread and infect theentire network.

Any PC that has access to theInternet, receives Email, can accessinformation on a CD-ROM/Diskette, oris connected to a network withanother PC that can perform any oneof these functions is at risk.

The results of a virus infecting a PCcan range from minor annoyances toall data stored on the PC’s hard drivebeing erased. A format and recoverymay be required in order to completelyclean the PC, and some files may bepermanently lost. The recoveryprocess could last a week or more,which would have a direct impact onbusiness.

It is a dealer’s responsibility to havea virus engine (McAfee or Norton) andalso the most current definition file forthat engine to work with on eachTechline client.

The base engine can be purchasedfor $30-40 at such retail outlets asBest Buy, Circuit City, Comp USA, etc.

However, installing the anti-virusengine alone is not enough for properprotection. The definition file needs tobe updated on a weekly basis. Thedefinition file provides the protectionfrom new viruses. The latest definitionfiles can be located athttp://www.mcafee.com for McAfeeusers or http://www.symantec.com forNorton users.

All PCs purchased from PC Sourceand GM Dealer Equipment comepreloaded with a virus engine. Thedefinition files will still need to beupdated.

In order to assure protection fromthe Nimda virus, your anti-virussoftware should be dated no earlierthen 9/19/2001. Once updated to thislevel, updates should be done on aregular basis. If GM is required toassist in cleaning up a virus, thedealership will be billed accordingly.

For assistance with the virusprotection software, contact yoursoftware manufacture or visit their

web site at http://www.mcAfee.comor http://www.symantec.com

– Thanks to Sam Hutson

GM TechLink is a monthly magazine forall GM retail technicians and serviceconsultants providing timely informationto help increase knowledge about GMproducts and improve the performance

of the service department. Thismagazine is a companion to the GMEdge publication.

Publisher & Editor:

Mark Stesney

GM Service Operations

[email protected]

Technical Editor:

Jim Horner

[email protected]

1-248-816-3641

Production Manager:

Marie Meredith

Desktop Publishing:

Greg Szpaichler, MediaWurks

[email protected]

FAX number:

1-248-649-5465

Write to:

TechLink

PO Box 500

Troy, MI 48007-0500

GM TechLink on the Web:http://service.gm.com

General Motors service tips are intendedfor use by professional technicians, not a"do-it-yourselfer." They are written toinform those technicians of conditionsthat may occur on some vehicles, or toprovide information that could assist inthe proper service of a vehicle. Properlytrained technicians have the equipment,tools, safety instructions and know-howto do a job properly and safely. If acondition is described, do not assumethat the bulletin applies to your vehicleor that your vehicle will have thatcondition. See a General Motors dealerservicing your brand of General Motorsvehicle for information on whether yourvehicle may benefit from the information.

Inclusion in this publication is notnecessarily an endorsement of theindividual or the company.

Copyright© 2001 General Motors Corporation

All rights reserved.

One of the easiest tests to run on theClass 2 bus is a voltage check, using aDVOM in normal DC volts mode. In aproperly operating vehicle, the DVOM willdisplay a low voltage, around 1 volt, butwill vary depending on the activity on thebus.

The Class 2 bus is held at groundpotential until a controller sends amessage, at which time it toggles thevoltage up to 7 volts for as little as 64microseconds. Because the majority of thetime the bus is at ground potential, using aDVOM in normal mode to measure a

normal operating Class 2 bus circuit willdisplay a reading between 0.7 and 1.5volts.

TIP: These values will vary dependingon the position of the ignition switch andthe number of controllers on the vehicle.

If the Class 2 bus is shorted to ground,the DVOM will display a consistent 0 volts.If it is shorted to battery, it will displaybattery voltage. This would typically causea No-Start or No-Start/No-Crank condition.

– Thanks to Mark Harris

PC Viruses Are Still a Concern

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http://www.mcafee.com/

http://www.symantec.com/










camshaft to be changed, dependent onneed. At idle and low engine load, overlap isminimum, improving idle quality. At higherengine speed and load, overlap is increased,allowing emissions to decrease.

General Motors Continuously Variable Cam Phaser

The 2002 4.2L RPO LL8 (VIN S) is thefirst General Motors application for acontinuously variable cam phaser (CVCP).The CVCP is a hydro-mechanical device thatregulates the position of the exhaustcamshaft relative to crankshaft position.

The CVCP system consists of two majorassemblies:

– Control Valve

– Cam Phaser

CVCP System Operation

The control valve is positionedhorizontally on the forward left side of the

cylinder head. It receives oil pressure fromthe oil pump by way of a port in the cylinderhead. The PCM operates the control valveusing pulse-width-modulation, according toinputs from the crankshaft position sensor

and MAP sensor. Oil pressure that isregulated by the control valve is thendirected to a port in the cylinder headleading to the camshaft and cam phaserpiston.

The exhaust cam gear is integral with thecam phaser and is located on the end of theexhaust camshaft. The piston within thecam phaser interfaces with the camshaftand cam phaser sprocket by helical splines.The piston within the cam phaser is springloaded to maintain an advanced positionwithout oil pressure from the control valve.As oil pressure from the control valveincreases, due to an increase in pulse width,

the piston is moved within the cam phaser,causing it to ride along the helical splinesand compress the spring. This action causesthe cam phaser gear and the camshaft tomove opposite of each other, retarding thecam timing.

CVCP System Service

Refer to SI 2000 for details. These arethe highlights.

Access to the cam phaser (proper

terminology is Exhaust Camshaft PositionActuator) requires removing the intakemanifold and camshaft cover.

IMPORTANT : It is critical not to losetension on the chain when replacing thephaser.

Chain Holding Tool J-44217 consists of

hooked rod, a block and a wingnut. You wneed to hook one tool into the chain oneach side of the engine to maintain tensioon the chain.

SI 2000 explains how to get thecamshaft, phaser (actuator) and chain bacinto correct timing. The camshaft actuatomust be fully advanced during installationEngine damage may occur if the camshafactuator is not fully advanced.

TIP : The labor operation for the solenois J0822. And the labor operation forreplacing the actuator (phaser) is J0823.

– Thanks to Kevin Ho

and Randy Pe

Cam Phasing Technology continued from page 1

Cam Phaser

Cam Phaser Schematic

Control ValveRemoving the cam phaser (actuator) Chain Holding Tool J-44217 in place

Cam Phaser Operation

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What are they and why doI care?

Simply put, power modes are the basisfor all module operations on today’svehicles. As we respond to customerdemand for features, we add to the

complexity of the vehicle operations. Wealso add to the demands we place upon thebattery and electrical generation systems ofour vehicles. A way to control this demandis to turn on only certain features at any onetime. This is accomplished with powermodes.

A traditional power modeexample

The power mode signal may be assimple as a battery positive voltage inputwired to a particular ignition switch contact.If this is also the battery positive voltagesupply to the module/device, the module/

device will operate only with the ignitioncontact closed to battery positive voltage.

An example of this is the starter relaywhen it is wired directly to theCRANK/START contact of the ignitionswitch. When the CRANK/START contactsare closed, the starter relay is energized andprovides a current source to the starter andstarter solenoid. When the ignition switchleaves the CRANK/START position, theswitch contacts open and the starter relay isde-energized. This removes the currentsource from the starter and solenoid andthe starter operation stops.

Power mode definedThe power mode is the information used

by the various control modules on thevehicle to determine operation. If a controlmodule does not receive a power modesignal (either a serial data message or a hardwire input) the control module does notoperate.

On a vehicle utilizing a module for powermode control, no operations using two ormore modules are possible without a powermode decision by the power mode master(PMM) and a power mode message fromthe PMM. The possible power modes are:

– OFF-ASLEEP: no activity on the serial

data circuits; the modules are asleep andin their minimum power usage state

– OFF-AWAKE: activity on the serial datacircuits; the modules are awake andexpecting either serial data or hardwireinputs

– RAP: those modules that have functionsenabled in Retained Accessory Powerare fully operational; the rest will be OFF-AWAKE

– ACCESSORY: those modules that havefunctions enabled in ACCESSORY arefully operational; the rest will be OFF-AWAKE

– RUN: all modules are fully functional

– CRANK: those modules that have nofunction critical to engine starting areOFF, to provide maximum power forcranking and starting operation and tolimit customer concerns, i.e. audiosystem noise.

Power mode masterOn vehicles that have several control

modules connected by serial data circuits,one module is the power mode master(PMM). On all vehicles, the PMM is a bodycontrol module. The specific body controlmodule used depends upon the vehicleconfiguration and system architecture.Possible PMMs are:

– Body Control Module (BCM)

– Dash Integration Module (DIM)

– Instrument Panel Module (IPM)

– Instrument Panel Cluster (IPC)

The PMM receives inputs from theignition switch and uses these inputs todetermine the proper power mode. Todetermine the correct power mode thePMM uses:

– The state of these signals/circuits, eitherswitch closed = 1 or switch open = 0.

– The sequence of switch closuresreceived by the PMM.

– The status of the engine run flag, a serialdata message.

In the following example, the PMMreceives three signals/circuits from theignition switch. These are the Unlock (IGN

0), Run/Crank (IGN 1) and Crank ignitionswitch signals/circuits. The chart belowindicates the modes detected andtransmitted by the PMM using this three-wire ignition switch input configuration:

Ignition switchsignal/input errors

As with any circuit, the ignition switchinputs can be open circuited/shorted toground, shorted to battery voltage or

shorted to another ignition switch circuit.We will examine each circuit for each errorcondition below.

Fail-safe operationBecause the operation of the vehicle

systems depends on the power mode,there is a fail-safe plan in place if the PMMshould fail to send a power mode message.The fail-safe plan covers those modulesusing exclusively serial data control of

power mode as well as those modules withdiscrete ignition signal inputs.

Serial Data Messages

The modules that depend exclusively onserial data messages for power modes stayin the state dictated by the last valid PMMmessage until they can check for the enginerun flag status on the serial data circuits. Ifthe PMM fails, the modules monitor theserial data circuit for the engine run flagserial data. If the engine run flag serial datais true, indicating that the engine is running,the modules fail-safe to RUN. In this statethe modules and their subsystems can

support all operator requirements.If the engine run flag serial data is false,

indicating that the engine is not running, themodules fail-safe to OFF-AWAKE. In thisstate the modules are constantly checkingfor a change status message on the serialdata circuits and can respond to both localinputs and serial data inputs from othermodules on the vehicle.

Discrete Ignition Signals

Those modules that have discreteignition signal inputs also remain in the statedictated by the last valid PMM messagereceived on the serial data circuits. Theythen check the state of their discreteignition input to determine the current validstate. If the discrete ignition input is active,battery positive voltage, the modules willfail-safe to the RUN power mode. If thediscrete ignition input is not active, open or0 voltage, the modules will fail-safe to OFF-AWAKE. In this state the modules areconstantly checking for a change statusmessage on the serial data circuits and canrespond to both local inputs and serial datainputs from other modules on the vehicle.

Power Modes

Ignition Switch

PositionOFF

Unlock

Accessory

RUN

Crank

OFF from RUNor Accessory

Engine Run

Flag State0

0

0

0

0

0

Crank

0

0

0

0

1

0

Run/Crank

IGN 10

0

0

1

1

0

Unlock

IGN 00

0 to 1

1

1

1

1 to 0

Power Mode Transmitted

OFF-ASLEEP Opening adoor or pressing a key fobbutton changes this toOFF-AWAKE.

Unlock (OFF-AWAKE)PMM then transitions toAccessory

Accessory

RUN

Crank

RAP Opening a door or aninternal timer cancels thispower mode.

Sampled Ignition Signal States (with the engine not running)

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Diagnosis of power modeerrors

TIP: Not all vehicles support all PowerModes, and those vehicles that do notsupport all power modes may cause theTech 2 to display a false loss ofcommunication screen, followed oraccompanied by beeping. This condition isconsidered normal.

Beginning in July 2001, all subsystems

affected by power mode should have addeda step to their Diagnostic System Check toverify the power mode as sensed andtransmitted by the power mode master(PMM). This is accomplished through a newfeature on the Tech 2. Follow this path onyour Tech 2 to reach this feature:

– Diagnostics

– Model Year

– Vehicle Type

– Diagnostic Circuit Check

– Class 2 Power Mode

While in this function, rotate the ignitionswitch through all positions. The Tech 2should display all power modes as theignition switch signal is processed by thePMM and transmitted on the serial datacircuits.

IMPORTANT: The engine may startduring this procedure.

Depending upon the PMM programming,

and whether or not you have all of the doorsclosed, you can expect to see the followingdisplayed as you rotate the ignition switchfrom OFF, through all positions and back toOFF:

– Off / Off-Awake

– Unlock / Off-Awake

– ACC / Accessory

– RUN / ON / Run / On

– CRANK / Crank

– RUN / ON / Run / On

– ACC / Accessory

– Unlock / RAP

– RAP

– Off / Off-Awake

IMPORTANT: You must see some variof the bolded items listed above matchedthe appropriate ignition switch position. Ifyou do not see the appropriate power momatched to the ignition switch position, th

new step in the subsystem diagnosticsystem check will direct you to a PowerMode Mismatch test located in the BodyControl System service category. This newtest will diagnose the root cause for theconcern.

TIP: RAP will not be displayed if youhave the driver door open or if the PMMdoes not support that function.

– Thanks to Bob Kee

Circuit

Crank

IGN 1

IGN 0

Error

Open / Shorted to ground

Shorted to Voltage

Shorted to IGN 1

Shorted to IGN 0


Shorted to Voltage

Shorted to Crank

Shorted to IGN 0


Shorted to Voltage

Shorted to Crank

Shorted to IGN 1

Affected Functions

Radio/Audio SystemHeated SeatsPower SeatsPower Windows












OnStarHVACPower MirrorsAutomatic Lighting












Possible Customer Complaint

Noisy audioBattery draw with these options ON and operating in Crank may cause ano crank conditionRAP will function normally.

These features will be inoperative. The PMM senses a Crank condition ansends the Crank power mode message with the ignition switch in the RUand Accessory positions.There will be no RAP functionality.

These features will be inoperative with the ignition switch in RUN.Those features that operate in Accessory will operate correctly in theACCESSORY ignition switch position.RAP will function normally.

These features will be inoperative with the ignition switch in RUN.Those features that operate in Accessory will not operate correctly in theACCESSORY ignition switch position.There will be no RAP functionality.

Inoperative in RUN ignition switch position, unless the feature operates inAccessory. Those features that operate in Accessory will operate correctlyin the ACCESSORY ignition switch position.RAP will function normally.

All modules remain ON-AWAKE at all times, all automatic features ON at atimes, causing dead battery.High current draws in CRANK, possible no crank condition.There will be no RAP functionality.

All features fully functional only in CRANK ignition switch position.RAP will function normally.

All features fully functional in UNLOCK, ACCESSORY, RUN and CRANKignition switch positions. Possible dead battery if ACCESSORY positionused for extended periods.There will be no RAP functionality.

All features operational only in RUN ignition switch position.There will be no ACCESSORY functionality.There will be no RAP functionality.

All features operational in ACCESSORY ignition switch position will be ONat all times. Possible dead battery and a no-crank/no-start condition.Full feature operation in RUN ignition switch position.There will be no RAP functionality.

There will be no ACCESSORY functionality.There will be no RAP functionality.

All RUN features are operable in Accessory position, no discrimination ofaccessory only features.There will be no specific ACCESSORY functionality.There will be no RAP functionality.

Ignition switch signal/input errors chart

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EVAP System Tester

6

In the past, when you’ve needed to locatea leak in a vehicle’s EVAP system, you’vepressurized the system with your EVAP

Pressure/Purge Diagnostic Station J-41413,and listened for leaks with the UltrasonicDetector Kit J-41416.

Why a New Detector isNeeded

New government regulations require allcars and light duty trucks to be capable ofdetecting EVAP system leaks of 0.020-inch orgreater in the near future. GM beganimplementing this capability on some 2000models, with more models added each year.The sound created by a leak this tiny is veryhard to locate using the existing testequipment, especially in the noisy conditions

of a service department.

The SolutionAbout the time you read this, you should

be receiving your new J-41413-200Evaporative Emission System Tester (EEST),which is an essential tool.

The EEST is designed to install in place ofthe the gauge panel in your existing J-41413Cart. Follow the instructions that come withthe kit.

What the Kit ContainsJ-41413-200 EEST Main Unit

J-41413-VLV EVAP Port Vent Fitting

J-41413-SPT Spotlight

J-41413-210 Operator Manual

504956 Ultra Trace™ SmokeProducing Fluid

Fuel Tank AdapterHooking up the EEST to the vehicle

requires one of the following adapters. Theseadapters are previously released essentialtools, specific to various vehicle lines, sothey are not included in the EEST kit. Theadapter screws into the fuel tank filler neck,and the fuel cap screws into the adapter.Finally, the EEST is connected to the adapter.

Refer to SI 2000 to determine whichadapter to use.

J-41415-10 Shallow Cam Type

J-41415-20 Deep Cam Type

J-41415-30 Threaded Type

J-41415-40 Quarter Turn Type

Using the Tech 2You also need to use your Tech 2 when

using the EEST to test the EVAP system. Innormal operation, a vent valve is open toallow fresh air to flow into the canister. Anelectrical solenoid energizes to close theEVAP vent valve. The vent valve must besealed before the EEST can be used topressurize the system.

With key on, engine off, after "building"the vehicle on the Tech 2, under thePOWERTRAIN section:

– select F2: Special Functions.

– select F0: Engine Output Controls

– select F1: EVAP System

– select F2: EVAP Vent Solenoid.

This will allow energizing the ventsolenoid to seal the EVAP system.

How the EEST Tester Works

The EEST creates an inert, non-toxicwhite smoke by heating and vaporizing aspecial mineral oil supplied with the kit.Nitrogen from the EVAP Cart carries thesmoke under low (1/2 psi, or 13-in. H2O)pressure to the fuel tank adapter. Theadapter is installed to the fuel filler neck ofthe vehicle, and the fuel filler cap is installed

to the adapter. This permits checking theintegrity of both the EVAP system and thefiller cap at the same time.

TIP : The low pressure applied to theEVAP system by the EEST is measured ininches of water (in. H2O), not the morecustomary inches of mercury (in. Hg.) Thereis a significant difference in scale betweenthese two measuring systems.

TIP : The pressure gauge on the EESTindicates total pressure in the EVAP system.The tester applies a maximum of 13 in. H2O.If the gauge reads higher than that, thedifference is likely from the vapor pressure ofthe fuel, which is present in any sealed

container of gasoline.TIP : The EEST does not use the

underhood EVAP system connector.Exceptions are noted in SI 2000.

Once the EVAP system is filled withsmoke, you’ll use the spotlight to inspect alllines, fittings, and components in the EVAPsystem. Look for a plume of smoke, whichwill be emitted from the leak location.Although the spotlight is powerful, you’ll getthe best results by using it under subduedlight. (That means, don’t use it in directsunlight.)

TIP : Be sure to turn off fans and closedoors to protect the vehicle from breezes,

which will disturb the smoke.When you locate the leak, perform

conventional repairs. Then, use the EVAPService Bay Test or the EEST’s built in flowmeter to check your work.

Additional FeaturesThe spotlight is powered by a rechar-

geable battery, so it’s extremely portable,

If the vehicle being tested does notsupport the EVAP Service Bay Test, the EESTcontains test orifices for both 0.020-inch (0.5mm) calibrated vehicles and 0.040-inch (1.0mm) calibrated vehicles. Refer to Bulletin 01-06-04-044 to determine the correct test

orifice to use for the vehicle being tested.

Attach the hose to the appropriate testorifice, press the remote button to activatenitrogen flow, and align the flow meter’s redflag with the float. Then reattach the hose tothe vehicle and pressurize the EVAP system.The time necessary to fill the system willvary depending on fuel tank size and fuellevel. Once the float on the flow metersettles, compare its position to the redarrow. If the float is above the arrow, furtherrepair is needed. If the float is below thearrow, repairs are satisfactory.

– Thanks to Mike Sculthorpe and Jack Woodward

Smoke Producing Fluid, 16 oz.Fuel Tank Adapter

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The February and March 2000 issuesof TechLInk brought you information onhow the GM oil life system works, andhow to reset it in various vehicles. Youmay wish to review this information onthe TechLink web page, athttp://service.gm.com.

Briefly, engine oil degrades in apredictable fashion, according to severalmeasurable engine operating conditions.The engine control module countscombustion events (measured in rpm)and reads coolant temperature. Fromthese numbers, the computer is able totrack oil deterioration and notifies thedriver when a change is needed.

The best value from the cost of an oilchange is obtained by maximizing themileage between changes, so long asthere is no adverse effect to the engine.With the GM oil life system, the average

person can expect oil change intervals of4000-7000 miles for mixed driving, and7000 to 10000 miles for highway driving,while the Chevrolet Corvette and the2002 Envoy, Bravada and TrailBlazer canachieve 15000 miles under idealconditions.

Since the GM oil life system firstappeared on some 1988 Oldsmobiles,over 10 million have been built,presently at the rate of over 3 million a

year. By model year 2003,GM expects to install oil lifesystems on essentially allcars and light duty trucks.

This past May, the GMoil life system development

team was honored byreceiving the first everEnvironmental Excellencein Transportation awardfrom the Society ofAutomotive Engineers. Thisaward recognizes that theextended range offered bythe oil life system can savehuge amounts of new oil,and can keep thousands ofgallons of used oil out ofthe environment.

There’s a lot of information on vehiclemaintenance shared on consumer-

oriented websites – some correct, comeerroneous, and some simply outdated.For instance, conventional wisdom callsfor oil changes every 3000 miles. Notsurprisingily, this conservative figure isalso supported by those who deriveincome from selling oil changes. Manyof your customers have becomeconvinced that any longer oil changeinterval is somehow harmful to theirengine.

At the retail level, you can do yourpart by promoting proper use of the Goil life system. Become familiar with it

function, and be prepared to helpcustomers understand that observingthe montor’s recommendation is theeasiest way to take the guesswork ouof oil change intervals. It also ensuresthat they are giving their vehicle theproper care it deserves, at the minimuexpense.

– Thanks to David Staand Chuck Bu

GM Oil Life System Revisited

Affected Vehicles:

– 1997-2002 Chevrolet Cavalier

– 1998-2002 Oldsmobile Intrigue

– 1999 Buick Regal

– 2000-2002 Buick LeSabre, CadillacDeVille and Seville, Chevrolet Impalaand Monte Carlo, Pontiac Bonnevilleand Sunfire

– 2001-2002 Buick Regal, OldsmobileAurora

Some customers may comment on a

clunk noise from the front of the vehiclewhen turning. This condition may also befelt throught the steering wheel whenturned from stop to stop with the vehiclestationary. The clunk may be heard at 180°or 360° of wheel rotation in eitherdirection.

This condition is commonlymisdiagnosed as originating in the steeringgear. Actually, it may be caused byinadequate lubrication of the steeringintermediate shaft.

These are the highlights. A detailedbulletin will follow.

Remove the intermediate shaft andlubricate it with Kit GM P/N 26098237.

With the shaft fully extended, dispensethe full contents of the kit syringe into thealuminum end of the yoke opening. Usethe rubber stopper in the kit to plug theyoke opening. Swing the upper yoke 90°to retain the rubber plug while you

collapse the shaft as far as possible. Witthe plug removed, extend the shaft andinspect for minimum of 5 mm of greaseon the shaft splines.

TIP : Stroke and extend the shaft atleast 15 times before installing to thevehicle.

– Thanks to Gary McAd

Clunk During a Turning Maneuver

How Driving Style Affects Oil Life

Dispensing Lubricant Collapsing Shaft to Distribute Lubricant.

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This review of service bulletins releasedthrough mid-October lists the bulletinnumber, superseded bulletin number (ifapplicable), subject and models.

GENERAL INFORMATION:01-00-89-013; Correct Use of Labor

Operation R4490, RKE Transmittter,Replace; 2002 and Prior Passenger Carsand Light Duty Trucks

HVAC:01-01-38-010; Noise When A/C

Selected and Rear Fan On (ReplaceAuxiliary Thermal Expansion Valve); 2001Chevrolet Venture, Oldsmobile Silhouette,Pontiac Montana with Rear Auxililary AirConditioning (RPO C69)

STEERING:01-02-32-007; Accessory Drive Belt

Whine (Reposition Power Steering Pump

Pulley); 2001-02 Chevrolet and GMMC C/K1500 Series Utility Models

SUSPENSION:01-03-07-001; Revised Wheel

Alignment Specifications, Rear CamberAdjustment (AWD) and Rear ToeAdjustment; 2002 Buick Rendezvous,Chevrolet Venture, Oldsmobile Silhouette,Pontiac Montana, 2001-2002 Pontiac Aztek

01-03-10-005; Wheel Squeak (InstallWheel Cover Insulators); 2000-2001Chevrolet Cavalier, Pontiac Sunfire

DRIVELINE AXLE:99-04-20-002A; replaces 99-04-20-002;

Driveline Clunk; 2002 and Prior Light DutyTruck Models

99-04-21-004A; replaces 99-04-21-004;Discontinue Flushing and ReplacingTransfer Case Fluid Due to Bump/ClunkConcerns; 1998-2000 Chevrolet and GMCK1-2 Pickup and Utility Models, CadillacEscalade, with NP246 Automatic TransferCase (RPO NP8)

01-04-17-003; Propeller Shaft and RearDrive Axle Diagnostic Information; 2001Chevrolet Camaro and Pontiac Firebird

BRAKES:01-05-22-003; Revised Vacuum Brake

Booster Replacement Procedure; 1999-2001 Chevrolet Corvette with TelescopingSteering Column (RPO N37)

ENGINE/PROPULSIONSYSTEM:

99-06-04-005B; replaces 99-06-04-005A;Driveability Symptoms Due to CloggedFuel Injectors (Clean Injectors); specifiedcar models 1994-1999 with 3.1L or 3.4LEngine (VINs E, J, M -- RPOs LA1, LG8,L82)

01-06-01-025A; replaces 01-06-01-025;Correct Oil Viscosity and Oil Filter Usagefor the Duramax 6600 Diesel Engine (RPOLB7); 2001-2002 Chevrolet Silverado andGMC Sierra 2500HD and 3500 Modelswith 6.6L Engine (VIN 1 -- RPO LB7)

01-06-04-037A; replaces 01-06-04-037;Fuel Transfer Pump Inoperative (ReplaceFuel Transfer Module); specified Chevroletand GMC Medium Duty Models between

1990 and 200101-06-04-042; Revised Engine Cooling

Fan Ground Circuit Information; 1999Chevrolet Malibu, Oldsmobile Cutlass withV6 Engine

01-06-04-043; Revised DiagnosisTrouble Codes (DTCs) P0404, P0405,P1404; specified 1998-2000 Truck models

01-06-125-002; Check Vehicle MessageDisplayed on Charger, Battery Pack ControlModule DTC 267 Set (Replace andRelocate Airflow Sensor); 1997-1998Chevrolet S-10 Electric Trucks With Lead-Acid or NiMH Battery Packs

TRANSMISSION/TRANSAXLE:

01-07-29-005; Eaton and Spicer ManualTransmission Unit Repair Information; 2002and Prior Chevrolet and GMC MediumDuty Trucks with Eaton or Spicer ManualTransmission

BODY AND ACCESSORIES:01-08-46-002A; replaces 01-08-46-002;

Programming of Replacement On-Star®

Vehicle Communication and InterfaceModules (VCIM); 2002 Buick Century,Regal, Cadillac DeVille, Seville, Chevrolet

Impala, Monte Carlo, Oldsmobile Aurora,Intrigue, Pontiac Bonneville, Chevrolet and

GMC S/T Utility Models, OldsmobileBravada

01-08-50-010; Seat Back ReclinerReplacement; 1998-2000 Chevrolet andGMC S/T Models, Oldsmobile Bravada

01-08-50-011; Memory Power SeatInoperative (Replace Memory Seat Module

with New Design Module); 2002 Chevroletand GMC S/T Utility Models, 2002Oldsmobile Bravada, built before specifiedVIN breakpoint

01-08-56-004A; replaces 01-08-56-004;Security Lamp Illuminated on the IP,Engine Stalls, No Start, DTC B2960(Security System Sensor Data Incorrectbut Valid) Set (Inspect and Repair Cause ofDTC B2960); 1998-2001 Chevrolet andGMC C/K Pickup and Utility, 2001Chevrolet and GMC C/K 3500 HD Pickup;1999-2001 Cadillac Escalade

01-08-58-004; Windnoise or GapBetween Luggage Carrier Side Rail Front

Cover and Roof Sheet Metal (Secure FrontSide Rail Corners and/or Reposition CrossBows); 2002 Chevrolet and GMC S/TUtility Models, Oldsmobile Bravada

01-08-62-002; Protective BumperCoating Applied to Prevent Stains BeforeVehicle Delivery to Customer; 2002Chevrolet Tracker LT

01-08-63-004; Creaking or Popping TypeSound from Front End or SuspensionWhen Driving Over Bumps or in TightTurns (Remove Road Debris from BetweenFront Inner Fender and Strut Support);1999-2002 Chevrolet Tracker (Both Two-and Four-Door Models)

01-08-66-007; Center High-Mount StopLamp (CHMSL) Applique Loose (Re-TapeApplique); 2002 Chevrolet and GMC S/TUtility Models, Oldsmobile Bravada

RESTRAINTS:01-09-40-003; Second Row Seat Belt

Latch Plate Rattle Prevention; 2001-2002Chevrolet and GMC C/K Utility Models,2002 Cadillac Escalade

01-09-41-007; Side Impact Air BagInflator Module Replacement; 2000-2001Buick Century, Regal, Chevrolet Impala,Monte Carlo

01-09-41-008; Side Impact Air Bag

Inflator Module Replacement; specified1997-2001 Cars and Trucks

Some 2002 Intrigues built before VIN2F124430 with Dimensional Sound System,option code UQ3, may have audio outputthat is below normal. The stereoequalization functions may also beinoperative.

This condition may be caused by an extraground wire in the IP harness. The wire is

providing a ground signal to the radio AMPSENSE circuit making it think there is anAudio Amplifier. This causes the radio unitto drop off its audio output to 10 to 14 dBless than normal operation, and equalizationfunctions are disabled.

To repair this condition, remove the radiohead and remove the Blk/Wht ground wire

at terminal B6 of connector C1. The VINbreakpoint above indicates when the new IPharness went into production. However, theassembly plant reworked harnesses andcontained vehicles prior to this point, so notall vehicles ahead of this VIN may beaffected. A service bulletin will bepublished.

– Thanks to John Woodrich

Bulletins – October 2001

2002 Intrigue Radio Audio Output Too Low

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