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1. Some customers may inquire about replacing the factory radio with an aftermarket setup or with an uplev el factory unit The days when a radio was a self contained box are long gone The first major change was the use of the Delphi Entertainment and Comfort bus Now on some of the newest vehicles the entertainment system is integrated into the vehicle s serial data network This means that the radio must be capable of communicating over the serial data bus also called class 2 with vanous other modules in the vehicle When a conventional radio is turned off it is truly off A radio unit in the senal data system however only looks off when it is tumed off Various circuits remain aware of what s going on and will wake up ata moment s notice For instance the chimes and OnStar both use the Reminder How to Access GM Training Courses on the Web radio speakers and will operate even if the radio function is turned off In a serial data system all mod ules check the state of health of all other modules so removing one mod ule will have a widespread effect on the entire network See the accompanying sidebar for a list of 2002 vehicles that do not use the serial data bus Using the 2002 Envoy as an exam ple here are some consequences of swapping the factory radio for an incompatible aftermarket unit Radio is inoperative Hard code set in diagnostics due to r2. F4 Diagnostic Circuit Check You ll notice that there are three choices here FO Class 2 DTC Check F1 Class 2 Message Monitor F2 Power Mode Systen Selection Henu Ar 1999 Bessemer lar Powertrain Body I Chassis 4a Diagnostic Circuit Check Tech 2 Menu The Class 2 DTC Check will poll all of the controllers on the bus to see if they have stored DTCs The properly operating controllers will respond Yes or No The Tech 2 will then display all the controllers who are currently communicating along with their answer The Class 2 DTC Check won t tell you what the codes are only if the controller has codes or not It will be up to you to navigate to each of the controllers and read their DTCs When a controller displays Yes the DTC can be either a current code ora history code Be sure to check both In all cases the next step is to go to the controllers that reported Yes they have codes stored and write them down For our purposes we re only con Example U1016 Loss of Communication from PCM Digit What It Means U Universal Communication Code 1 GM Specific Code 016 This is the decimal ID of the controller no longer sending its State of Health Message in this case PCM cerned with those codes preceded by a U for instance a U1064 After this is done you should have a list of controllers and the codes they ve stored similar to Table 1 In case you ve wondered what the numbers of a
3. ken message is complete But until you are comfortable with the changes please listen carefully to the new prompts TAC recently sent a laminated quick reference card to your dealer i ship One side contains a road map through the prompts The other side va has a Strategy Based Diagnostic tem plate as a reminder to perform the basics and be prepared before calling TAC You may want to make copies of this reference card for each person who calls TAC Thanks to Reed McMillan Ghasiing 1 ase DAR Bada GM TAC 1 Wenhicia inside the Budding l gt vi 1 877 446 8227 Pi ee ord TAC Consultant ae Fuel Injector Cleaning With high technology fuel systems and new internal components cleaning fuel injectors has taken on a completely different appearance from ten years ago In the past fuel injectors were frequently cleaned as routine maintenance often at every 12 000 mile service interval Some of the cleaners were so strong that they corroded the insulation on the coil windings of the injector And some cleaning systems that were not authorized by GM allowed injector cleaning chemicals to return to the fuel tank where they damaged sensitive fuel pump com ponents Recent testing of cleaners and the effect they have on fuel injec tors has indicated that the art of cleaning injec tors has evolved into an entirely new science Now it s recommended that injectors be cleaned only as ne
4. Equipment Options Chevrolet Impala police vehicles can be equipped with special equipment options SEO that you will not find on civilian vehicles If you encounter one of these vehicles during service or new vehilcle prep it s helpful to be able to recognize these modifications Otherwise you may attempt to repair a component which is actually functioning as intended TIP Check the Service Parts ID label inside the decklid It lists codes for all the factory installed special equipment on the vehicle SEO A98 Trunk Release The electric trunk release is set in the body computer to operate only with the ignition on SEO 6B2 Rear Door Handles Inoperative The rear door handle to latch operating rods are disconnected and reshaped The doors can be opened only from the outside SEO 6N5 Rear Windows inoperative The power leads to the rear window switches are disconnected and taped back The windows can be operated only from the driver s window switch SEO 6N6 Rear Door Locks inoperative The rear door lock rods are discon nected from the knobs The rear doors can be locked and unlocked only from the driver s door lock switch SEO WX7 Front Speaker Provisions The radio speakers in the front doors are not connected to the radio Instead a coil of wire is provided under the instru ment panel which permits connecting the front speakers to police installed commu nication equipment Radio ou
5. problem is usually easily repro duced and repeatable Because the problem is due to a con troller staying powered up when it s not Supposed to be the problem is usually a hard fault The fault can be caused by a short to power on the ignition feed circuit of the offending controller a power feed back through another component or it can be a problem within the controller itself whereas the controller is unable to power itself down This can be confirmed by comparing who is communicating in RUN with who is communicating in OFF D A battery drain concem may accompany the other complaint s Because a controller is remaining alive after the ignition has been tumed off the battery will slowly drain Most controllers can pull in excess of 1 amp when powered up and if the vehicle has n t been driven for a couple days the customer may have a no start condition This scenario tends to be pretty sim ple to locate and fix providing you ve noticed which controller has the U Codes set The controller with the U Codes is the one that is staying powered up when it shouldn t Using the Parasitic Load tool 38758 and a Fluke 87 you should be able to isolate the circuit that is supplying the unwanted current by pulling one fuse at a time until the controller powers down Final Thoughts Although not all Class 2 related prob lems will fit these scenarios you ll find that most of them will Your ability to rec ognize
6. reason each controller has a number of U Codes pointing at many other controllers is that the controller has come to expect a certain combination of controllers based upon the learned sources for messages which require fail soft action These are the State of Health messages IDs it has seen and when these are no longer seen the con troller sets the code s In this case after properly initializing the controller can t see anybody s State of Health message and therefore sets multiple U Codes Not all controllers will set the same number or combination of U Codes A controller will only set U codes for those modules that it needs information from For instance if the BCM doesn t need any information from the ABS controller the BCM wouldn t set a U1041 Loss of communication from ABS because it wouldn t care E The customer concem may deal with IP lights intermittently coming on then off The radio may intermittently stop playing HVAC may become inter mittently inoperative or display blinking Customer may have an intermittent No Start condition You can also expect the security indicator to show some reaction You should also have DTCs like P1626 andB3094 as well as the U1001 U1254 DTCs Each controller relies on the informa tion it receives from other controllers to function properly If a controller doesn t get the proper information it has to go Into a default mode and set the appropn ate U Code This can also
7. U Code represent the chart above shows the structure of the U Codes Each controller on the Class 2 bus has its own unique ID number This ID number is sent out on the bus every 2 seconds as a State Of Health SOH message when the modules are awake to let the other controllers know that it s present and functioning For instance the PCM will send out its ID decimal equiva lent 016 and the BCM sends its ID deci mal equivalent 064 So when you notice that the BCM has set a DTC U1016 you know that the BCM originally received the SOH message from the PCM then didn t see the PCM s State of Health Message for 5 seconds or 2 5 times the expected SOH period of 2 seconds This is interpreted as a loss of PCM communi cations by the BCM If a control module does not receive required information when it initializes it will set either DTC U1000 or U1255 These DTCs indicate that one or more messages containing required data was not received A short to ground or volt age aS well as an open circuit in the class 2 serial data circuit may account for the U1000 or U1255 If the short or open was present intermittently when the control module initialized then the module received the required data later the DTC U1000 or U1255 would be stored as a history DTC Using this information we can now explore the three most common scenar ios Surrounding the diagnosis of Class 2 related faults Three Common Class 2 Scenarios When using t
8. adio receives the run power mode message it compares the VIN information stored in the radio to the VIN information received from a module on the serial data circuit responsible for transmitting that informa tion If a mis match occurs the radio dis play will indicate to the user that the radio is locked Once this takes place a DTC will set the radio will not respond to any button presses and will become inoperative Loss of chimes important audible sig nals to the driver Loss of remote playback devices if equipped There are three types of remote playback devices a multi disc remote CD changer a single disc CD player and a cassette player These devices may be factory installed or in some cases dealer installed All three devices have a wiring harness which plugs into the back of the radio The radio controls and communicates with the remote playback device through the data bus Replacing the Standard Factory Unit with an Uplevel Factory Unit Harnesses and hardware are specific to each level of radio Replacing a standard radio with a Bose unit for instance involves far more than just inserting a new radio unit into the instrument panel This is not recommended by GM Several dealer installed plug in remote playback modules are available however See the preceding section for details Radio Setup When the radio is tumed on it expects to receive the appropriate VIN information on the senal da
9. adio not being on the data bus Loss of steering wheel mounted control functions OnStar system will not work continued on page 2 or Begins With then type SI 2000 When the course information appears select View In J une we told you about the new web based SI 2000 training course just added to the Service Technical College cata log Here s how to get to the course You need to log into the Training Management System TMS at www gmcommontraining com If you have a past training history you should be in the TMS and can log in by using your Social Security Number as both your SSN and Password If you are not in the TMS or are having difficulties logging in call the Common Training Help Desk at 888 748 2687 Once in the TMS select the Catalog tab then select Catalog Search Select Course Number then select Is then type 10040 00W Click on the Submit button TIP You can also do a course name search by selecting Course Name Contains The next screen that appears contains the course description At the top left of the screen click on Take or Continue Course to access the SI 2000 web based training See the J une 2001 issue of TechLink for a description of how the course works Be sure to fill out the evaluation form at the end of the course to let GM know how you liked it TIP You need to have Flash 4 or newer to run the course Here are the instructions for obtaining the proper
10. cause a con troller to reset or reinitialize In most cases this is done without the cus tomer s knowledge However when the IPC reinitializes it may tum on a number of indicator lights for a bulb check The customer will notice this outward signal of the problem and will be the concern listed on the RO To correct the problem will require you to locate the source of the short to ground or power Easier said than done By using a Fluke 87 in Peak Min Max mode while wiggling the hamess you ll have a good chance of locating and cor recting the problem Scenario 2 A Smaller Percentage But More Than One Box Has U Codes Controller U Codes Set PCM Not Communicating ABS No DTC s BCM U1016 IPC U1016 Table 2 Scenario 2 If after developing the list you notice that a small percentage of the total num re Loe Fig 2 More Than One Box With Same U Code ber of controllers have U Codes Table 2 then the following items are typically true of your situation A The problem is a hard fault In this scenario chances are that the problem is current The problem can be readily duplicated When a controller goes down and Is unable to communi cate with other controllers the other con trollers go into a default or fail safe mode of operation For example if the PCM can t send fuel level data the IPC will default the fuel gauge to the Empty posi tion and set a U1016 The customer s complaint will be Fuel Gau
11. eded as deter mined by using the Strategy Based Diagnosis procedure GM has issued sever al bulletins about fuel injection cleaning 99 06 01 022 99 06 04 005 which was superceded by 99 06 04 005A and 00 06 04 003 All of these bulletins specify using the J 35800 A Injector Cleaner tool and General Motors Top Engine Cleaner GM TEC which ts now available in a new 24 ml container Tool J 35800 A is a cousin to the J 35800 which is a low pressure bug Sprayer container J 35800 A is a high pressure container which permits you to clean at pressures higher than vehicle sys tem pressures TIP When using J 35800 A follow the New 24 ml Bottle of GM TEC Specific cleaning procedures for each vehi cle platform Another specific feature developed for use with the J 35800 A is a smaller 24 ml bottle of GM TEC The part number for this new size bottle is 12346535 This P N is Currently available in the US only The use of J 35800 A and 12346536 has been made simple for you J ust add the correct number of pre measured 24 ml bottles of GM TEC to the J 35800 A tool then fill the remainder of the canister with gasoline and com mence cleaning TIP Find the proce dure for the vehicle you re cleaning then as instructed add either 1 bottle of 12346535 for 5 cleaner to 95 gaso line ratio or 2 bottles for a 10 cleaner to 90 gasoline ratio It is no longer necessary to find a graduated measurin
12. g cylinder in the shop and then hope that your mix ture is correct Delphi performed actual tests on fuel injec tion systems with GM TEC The findings are interesting If you do not use the correct amount of GM TEC you will not get positive results Using a smaller amount of GM TEC than recommended will not clean deposits from injectors Using too much cleaner actually leaves deposits behind Follow the cleaning pro cedure as outlined in either the bulletin or the service manual you don t need to concem yourself with playing chemist in the service bay Bulletin number 99 06 04 005 has been superseded by bulletin 99 06 04 005A The new bulletin changes the allowable concentration of cleaner from 5 to 10 Make sure you follow the 3 bulletin guidelines to determine which vehicles you can clean with the stronger concentration Bulletin numbers 99 06 01 022 and 00 06 04 003 address cleaning of poppet nozzles on CPI and SCPI units On SCPI units the poppets can stick shut occa sionally and cause driveability concems To determine if the poppet is stuck shut follow the Strategy Based Diagnostic pro cedures in the bulletin or service manual To unstick a closed poppet install tool J 44466 as outlined in the bulletin and then attach EVAP cart J 41413 J 41413 operates at pressures high enough to unseat a stuck poppet ball from the ball seat System pressures are not high enough to accomplish this J 41413 use
13. ge Inoperative B The U Codes stored are current If this is a hard fault then the U Codes are going to be stored as current The nice part of this scenario is that if you have current U Codes that are point ing to a specific controller then there are only a few things that can keep a offend Ing controller from communicating on the bus Loss of power to the controller Loss of signals required when deter mining the proper power mode Loss of ground to the controller Open on the Class 2 wire from the controller Can t be shorted because that would cause scenario 1 above or you wouldn t be able to communicate with the any of the controllers The controller itself is defective C The same U Code is stored in 2 or more of the controllers See Figure 2 When you see the same U Code stored in more than one box most of the time it s due to the fact that the con troller the DTC is pointing to is no longer able to communicate on the Class 2 bus For instance if the IPC and the BCM have both stored a U1016 then the IPC and BCM are trying to point to the controller that is at fault in this case the PCM It s very important that under these condi tions you look for common U Codes stored among different controllers Please note that the rules for dealing with multiple U codes are 1 Current before history unless told otherwise in the diagnostic table 2 The DTC repeated the most times 3 From l
14. he Class 2 DTC Check feature of the Tech 2 you will notice that In most cases your situation will fall into one of three categories 1 Most or all controllers report that Yes they have DTCs stored and are pre dominately U Codes See Table 1 and Figure 1 2 A smaller percentage of controllers 4 but more than one report that Yes they have DTCs set and are predomi nately U Codes See Table 2 and Figure 2 3 Only one controller reports that Yes it has DTCs set and are predominantly U Codes See Table 3 and Figure 3 These are general categories that are generic to all Class 2 equipped vehicles It will be up to you to properly apply this information along with your knowledge of the particular vehicle to make a proper diagnosis After you ve developed a complete list of codes you can see which scenario they fit into Scenario 1 Most Or All Controllers Have U Codes Set Controller U Codes Set PCM U104 truck or U 1040 car U 1064 U1096 ABS U1016 U 1064 U1096 BCM U1016 U1041 U1096 IPC U1016 U1041 U 1064 SDM U 1300 or U1301 or U1305 Table 1 Scenario 1 If after developing the list you notice that most or all of the controllers have Fig 1 All Controllers Have U Codes history U Codes then the following items are typically true of your situation In this scenano the source of the problem is most likely an intermittent Return to page 1 Short to ground or power A T
15. he problem is intermittent and because of this you have not been able to duplicate the complaint or have seen it infrequently The reason it must be intermittent is that if you can currently read the codes from the controller using the Tech 2 then the Class 2 bus is not currently shorted to ground or power Remember a hard Short to ground or power would render the Class 2 bus completely inoperative and no communications would occur between any controllers B At least one controller will have DTCs U1300 U1301 or U1305 set On all vehicles produced since M odel Year 2000 at least one control module will set DTCs U1300 U1301 or U1305 These DTCs point to an intermittent short to ground or voltage These DTCs must be diagnosed before attempting to diag nose any other DTCs The test table entitled Scan Tool Does Not Communicate with Class 2 Device located in the Data Link Communications service category Is being modified to address the problem of intermittent shorts to ground and voltage You can access this updated test table via SI2000 C The U Codes are history codes The DTCs are history because of the intermittent nature of the problem Once the State of Health messages are seen again each controller resumes normal operation and moves the DTCs over to history D The U Codes are pointing to a number of other controllers not just one other controller See Table 1 and Figure 1 for an example of this The
16. ild restraint LATCH system has been ina collision LATCH system parts may require replacement the applicable service manual and the parts catalog for more Information Thanks to J erry Garfield Refer to Bulletin 01 09 40 002 TETHER Typical child seat attachments using LATCH system Return to page 1 Diagnosing the 4T65E Transmission RPO M15 MN7 M76 This summarizes the latest diagnostic information for 4T65E transmissions used in 2000 2001 models 2001 Aztek 2000 2001 Impala Monte Carlo may also be possible on other models P0716 P0717 Misc Codes The subject codes may caused by the wire hamess leading to the main transmission connector being routed such that the connector is side loaded This is analogous to grabbing the har ness near the connector with one s hand and pulling to one side The terminals can get mis positioned in the connector and not make good contact This may result in the codes mentioned The cor rection is to re route the harness such that the connector is not side loaded Aztek harness indicating direction of side load Additional information is available regard ing the re route through TAC if neces sary M is positioned harness t 2000 2001 Model Intrigue Grand Prix Silhouette M ontana Venture P0717 PO716 or Possible P0748 Other Misc Codes Some cases have been reported continued on page 8 Dealing with Police Special
17. in number if applica ble subject and models GENERAL INFORMATION 01 00 89 011A replaces 01 00 89 011 Newe Technical Assistance Information Form 2002 and Prior Passenger Cars and Trucks HVAC 01 010 39 002 Noise in Engine Compartment with A C On A C System Inoperative Install Redesigned Rear A C Suction Hose Replace Compressor 2000 Chevrolet and GMC C K Utility Models with Aux Rear A C RPO C69 SUSPENSION 01 03 10 004 Spare Tire Cover Replacement 2001 Chevrolet Tracker ENGINE PROPULSION SYSTEM 01 06 01 007A replaces 01 06 01 007 Engine Coolant Consumption or Coolant Leak Inspect for M aterial Degradation Replace Intake M anifold various 1995 1998 vehicles with 3 8L Engine VIN K RPO L36 01 06 01 010A replaces 01 06 01 010 Polymer Service Pistons numerous mod els from 1996 2001 with 3 1L or 3 4L in VINs J M E RPSs LG8 L82 LA1 01 06 01 018 Engine Tick Noise at Valve Train Speed Loss of Power Replace Push Rod 2001 Chevrolet and GMC C K and G Light Duty Models 2001 Chevrolet and GMC B7 C6 C7 Medium Duty Models with 8 1L Engine VINs E G RPO L18 01 06 04 038 Engine Low Power Stall No Start Replace Modular Fuel Sender Assembly and Fuel Filter 2000 2001 Chevrolet and GMC S Pickup Models with 2 2L Engine VIN 5 RPO L43 01 06 05 003 Vibration or Rattle Type Noise in Exhaust System at Idle Install Exhaust System Dampener Assembly 1999 2002 Che
18. ntroller no other controllers have any U Codes stored See Table 3 F Fig3 One Box With M ulti U Codes Industry Innovations and Figure 3 Of the three scenarios this one tends to be the most difficult to fig ure out so a good understanding of what happens here is critical The following items usually surround this scenario A With ignition on the U Codes stored will go to history These codes may return to current once the ignition is turned to the off position and the other controllers have had a chance to power down In this scenario the controller with all the U Codes is staying powered up after all the other controllers have gone to sleep which stops them from sending a State of Health message In this exam ple the IPC is staying powered up after the other controllers have powered down and because the IPC expects to see the State of Health message from the others and doesn t it sets the U Codes Once the ignition is tumed back on the U Codes are sent to history because the IPC now sees the State of Health mes Sages from the newly powered up con trollers again B Depending on the vehicle con cerns with the IP HVAC or Radio can be noticed Reinitialization can occur when the problem controller sees the others State of Health messages again M any times however there will be no outward signs of this problem and the only reason the customer s vehicle is in is because of a dead battery C The
19. otor 1998 200 Chevrolet Camaro Pontiac Firebird 01 08 64 011 Power Window Inoperative or Operates Slow Replace Power Window Motor 1999 2002 Buick Century Regal Oldsmobile Intrigue Pontiac Grand Prix 2000 2002 Chevrolet Monte Carlo RESTRAINTS 00 09 40 001A replaces 00 09 40 001 Excessive Lateral Movement of Some Aftermarket Child Seats Replace Rear Seat Buckle 1997 2002 Chevrolet Venture Oldsmobile Silhouette Pontiac Montana 1997 1999 Pontiac Trans Sport where the MIL light has been on and one or more of the above codes have been set The wiring hamess near the accumu lator and compressor may have rubbed through on the surrounding components Repair the wiring as necessary and re route the harness to ensure the problem will not re occur 2000 2001 All Models with 4T65E PO0741 P0742 Condition Number 1 Technician is Unable to Duplicate the Code This may be caused by sediment making its way through the valve body Warranty data suggests that most of these vehicles never retum to the deal ership for this concem To ensure such vehicles don t come back do the follow ing Drive the vehicle fairly hard in all gear ranges including manual 1 2 and 3 to exercise the valve body Raise the line pressure using the Tech 2 If the code does not return it is likely the sediment causing the concern has been exhausted from the valve body and it is safe to return the vehicle to the customer Inspec
20. owest number DTC to the highest number DTC D Other seemingly unrelated con cerns might also be present for instance inoperative door locks or power win dows Because a controller is currently unable to communicate there will undoubtedly be other concerns In fact it s likely that looking for U Codes with the Tech 2 was not the first thing you thought to do As a general rule connect the Tech 2 to every vehicle regardless of the customer complaint and go to the Class 2 Diagnostic Circuit Check to get an overview of what the whole vehicle is seeing Keep track of the controllers that have codes and then visit these con trollers to display and write down the codes stored At this point you ll have a better understanding of what the entire vehicle is doing It only takes a minute continued on page 6 Return to page 1 but can save hours of frustration To correct the problem in this sce nario you ll have to figure out which con troller is unable to communicate on the Class 2 bus but your detective work Should have yielded a suspect It s now a matter of deciding why the controller is unable to communicate no power no ground open Class 2 circuit incorrect power mode signals or a defective con troller Scenario 3 Only One Controller Has U Codes Stored Controller U Codes Set PCM No DTCs ABS No DTCs IPC U1016 U1041 U1096 Table 3 Scenario 3 There are multiple U Codes stored in only one co
21. rks com FAX number 1 248 649 5465 Write to gt lt TechLink PO Box 500 Troy MI 48007 0500 GM TechLink on the Web http service gm com General Motors service tips are intended for use by professional tech nicians not a do it yourselfer They are written to inform those techni cians of conditions that may occur on some vehicles or to provide informa tion that could assist in the proper service of a vehicle Properly trained technicians have the equipment tools Safety instructions and know how to do a job properly and safely If a con dition is described do not assume that the bulletin applies to your vehi cle or that your vehicle will have that condition See a General Motors deal er servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information Inclusion in this publication is not nec essarily an endorsement of the indi vidual or the company Copyright 2001 General Motors Corporation All rights reserved Return to page 1 Technical Assistance Center Phone Prompt Changes Effective J uly 30 2001 there was a change in prompts when contacting the Technical Assistance Center This change comes as a direct result of comments on the Dealer Survey and our desire to continually improve The new prompts will allow you to get to a consultant easier and more quickly As before the system allows you to make a selection before the spo
22. s nitrogen which is an inert gas It will not react with any clean ing chemicals or leave deposits on the poppet that you are trying to clean Using recirculating blocks J 44466 11 and 12 the fuel system is separated into J 44466 11 Fuel Line Recirculating Block two loops to allow cleaning and unsticking at the fuel meter body And the cleaning agent is not permitted to enter the vehi cle s fuel tank which could cause damage to the fuel pump check ball Separating the system into two loops also eliminates the need to disable the fuel pump while running the vehicle during the cleaning operation Thanks to Dan Wimer and Matt Hamilton Return to page 1 Demystifying Class 2 Diagnosis The Class 2 data bus allows con trollers like the Powertrain Control Module PCM to communicate with other controllers on the vehicle This sys tem of communication allows information to be efficiently shared among a number of controllers Class 2 communications also reduces the complexity of the har ness and allows for a more thorough integration of sub systems This article will help you understand this communication system by covering the causes for three common Class 2 problems Class 2 DTC Check To properly diagnose Class 2 related problems an understanding of the Class 2 Diagnostic Circuit Check is necessary Follow this path on your Tech 2 to reach this feature FO Diagnostics Model Year Vehicle Type
23. t passages 9a and 9b for clogging T Condition Number 2 Technician is Able to Duplicate the Code Generally speaking the diagnostics in the service manual will lead you down the correct path if the code can be repro duced The one notable exception is that passages 9a or 9b in the spacer plate may clog setting a code P0741 this will not set P0742 If normal diagnostics fail to correct a PO741 inspect these pas Sages A design enhancement is in process to change passages 9a and 9b from an 0 5 mm orifice and a slot to two 0 7 mm Slots You will see this new design sometime in mid 2002 production Please note that sometime during the 2002 model year P0742 in the 4T65E will change from a type A diag nostic code to a type B code This Should lessen the chance of an unneces sary code P0742 being set Thanks to Chris Anderson Return to page 1
24. ta line If this does not hap pen the radio will lock up A mismatch will occur under two circumstances 1 A radio is installed from another vehicle or a service replacement is installed 2 The module which communicates on the serial data circuit which supplies VIN information to the radio is replaced and not properly set up with the correct VIN information for that vehicle The only way to unlock the radio is by using a scan tool Follow the procedures in SI 2000 Thanks to Chris Edghill M ark install the appropriate Flash continued from page 7 Player to support their browser a Internet Explorer b Internet Explorer for AOL c Netscape Navigator With GM Online Obtain a local deviation from the GM Online site manag er and request an upgrade to Flash Player 4 0 or 5 0 Thanks to Chris Wallace aa Se ee ee ae a i J F pei i pe ee me a Fe GM TechLink is a monthly magazine for all GM retail technicians and Service consultants providing timely information to help increase knowl edge about GM products and improve the performance of the Service department This magazine is a companion to the GM Edge publication Publisher amp Editor Mark Stesney GM Service Operations Mark Stesney GM com Technical Editor J im Horner lt im Horner SandyCorp com 1 248 816 3641 Production M anager Marie Meredith Desktop Publishing Greg Szpaichler MediaW urks lt Spake mediawu
25. the circumstances surrounding each one of these scenarios and more importantly understand the reasons behind them will help your diagnosis to be more efficient Thanks to Mark Harris DLC Team by model year 2003 The When a vehicle with the The LATCH System LATCH is the industry stan dard acronym for the built in child restraint securing system Lower Anchorages and Top Tethers for Children LATCH consists of the top strap anchors in the vehicle as well as the built in lower anchors or receivers for LATCH equipped aftermarket child restraints What is new is the lower anchors The 2001 model year will begin the introduction of the lower anchors on Chevrolet Ventures and Silverado Pontiac Aztek Grand Am and Montana Oldsmobile Alero and Silhouette and GMC Sierra All rear seats in at least two seating positions will have it lower anchor is a bracket between the rear seat cushion and rear seat back The receivers are hooks that the LATCH equipped child seat can be attached to A LATCH equipped child seat may be secured in a vehi cle using the LATCH system Instead of the vehicle s regular seat belts LATCH equipped child seats may also be secured using the vehicle s regular seat belts Refer to the vehicle owner s manual for additional information on the LATCH system and securing a child restraint using the vehi cle s regular seat belts and also refer to the instructions that came with the ch
26. tputs that would normally go to the front speakers are now routed to the rear speakers so the audible key waming chime still functions Two important facts about the front door speakers each speaker has both a feed and wire and a ground wire and each speaker is rated at 10 ohms imped ance SEO 7Y6 Dome Lamp inoperative This feature causes the body comput er to ignore the signals from the mini wedge latches in the doors The dome lamp must be operated with the driver s master light switch SEO 6 4 Horn Inline Connector An inline connector with a wire loop is installed in the hom ground circuit This permits the owner to cut the loop and install a selector switch to permit operat ing the vehicle s siren with the horn Switch SEO UN9 Radio Interference Package Special spark plugs and wires are installed to reduce low fre quency interference with the police communication radio Standard Surveillance Switch This police car standard equip ment switch defeats the standard dome lamp radio display instru ment panel and PRNDL displays backup lamps and daytime run ning lamps not in Canada When operated this feature makes the police car less conspicuous All lighting functions can be manually activated if necessary Thanks to Erik J orgensen Return to page 1 August 2007 This review of service bulletins released through mid August lists the bulletin num ber superseded bullet
27. version of Flash Player for the SI 2000 course Without GM Online 1 Install the GM STC CBT Browser v2 0 CD is orange colored and labeled Install Disk for CBT Training version 2 0 March 2001 2 Or Visit www macromedia com downloads and continued on page 2 GM Service Operations continued from page 7 2002 Vehicles Without Serial Data Bus Radio Trucks Silverado Sierra Astro Safari GM C Series T Series S 10 Blazer Sonoma Cars Park Avenue Camaro Firebird Century Regal Grand Prix Loss of rear audio The audio amplifier is standard on some vehicle lines optional on most The radio supplies low level audio signals to the audio amplifier in order to boost the signal sent to the speakers The seral data circuit allows the radio to recognize that an amplifier is present Once the radio detects an audio amplifier it will output low level audio signals The audio amplifier is turned on when it receives a message via the seri al data circuit indicating that the radio is on Loss of built in Theftlock audio com ponent theft deterrence The after market radio will not have the protection of the GM Theftlock feature Theftlock is intended as a roadblock to switching radios from vehicle to vehicle such as would occur in case of theft Here s how it works The theft deterrent system utilizes serial data to determine if the radio is in the appropriate vehicle Each time the r
28. vrolet and GMC G Van ee with 4 3L Engine VIN W RPO L35 TRANSMISSION TRANSAXLE 01 07 30 024 Clearing Shift Adapts 2002 Chevrolet Cavalier Oldsmobile Alero Pontiac Grand Am Sunfire with 2 2L Engine VINs F 4 RPOs L61 LN2 and 4T40 E Automatic Transmission RPO MNA4 BODY AND ACCESSORIES 01 08 44 008 New Tool Availability for Antenna Mast Installation During Pre Delivery Inspection 2001 2002 Chevrolet and GMC C K Pickup M odels Silverado and Sierra Utility Models Tahoe Suburban Denali Yukon Yukon XL 2002 Chevrolet Avalanche 01 08 46 002 Programming of Replacement OnStar Vehicle Communicatoin and Interface M odules VCIM 2002 Buick Century Regal Cadillac DeVille Seville Chevrolet Impala Monte Carlo Oldsmobile Intrigue Chevrolet and GMC S T Utility Models TrailBlazer Envoy Oldsmobile Bravada With OnStar System 01 08 50 008 Power Seat Track Adjusters 2001 Buck Century Regal Chevrolet Impala Monte Carlo built after Specified VIN breakpoints 01 08 52 005 Remote Keyless Entry RKE System Does Not Function Properly Replace Receiver 2001 Buick Century Regal Chevrolet Venture Oldsmobile Intrigue Silhouette Pontiac Aztek Grand Prix Montana 2002 Buick Rendezvous 01 08 57 001 Carpet Wet in Front or Rear Footwell Apply Sealer to Rear Wheelwell 2002 Chevrolet Avalanche prior to J uly 1 2001 01 08 64 003A replaces 01 08 64 003 Window Motor Noise Replace M
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