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1. You may identify the Multec 2 by the Delphi insignia on the body The original Multec 1 has the RP lettering Electrical Testing of the Multec 2 The most likely reason for perform ing an electrical test is due to engine misfiring on one or more cylinders The electrical solenoid in the Multec 2 injector uses a high impedance coil This means it offers resistance to the electrical current flowing through it A change in resistance will have a corre Sponding effect on the operation of the injector Variations in fuel delivery can have an effect on driveability Some symptoms include rough idle or inter mittent misfire the kind that does not set a cylinder specific code You may think that the J 39021 Fuel Injector Tester and digital voltmeter would be useful in diagnosing the Multec 2 Actually the voltage drop test using the J 39021 and voltmeter was designed specifically for the Multec 1 and is not suitable for testing the Multec 2 Here s why In the Multec 2 the small wire Size and rapid heat build up within the coil will give erroneous readings of voltage drop Coil shorting is not a problem in the Multec 2 However in a very small number of cases the winding may develop a break When tested with the J 39021 this injector will actually pass the voltage drop test It is theorized that the high current of the J 39021 bridges the gap in the winding causing it to appear normal For this reason the b
2. matic transmission some customers may comment that the tachometer seems to indicate a significant drop in engine RPM during a prolonged decel eration in the form of a fluctuation or needle bounce The tachometer is responding to signals received during decel fuel shutoff Reprogramming the PCM to the latest calibration will cor rect the condition Head Restraint Migrates to the UP Position Owners of some 1997 2001 Buick Regal and Century Pontiac Grand Prix and 1998 2001 Oldsmobile Intrigue may comment that the head restraint does not stay in position on the seat but migrates to the full up position Remove the head restraint from the seat back by inserting a small diameter tool into the hole on each retainer and pressing Removing head restraint Firmly grasp each rod and rotate it 90 degrees Pull the rods out of the head restraint Turn the head restraint over and look into the hole where the head restraint installs to the post Locate the spring wire that fits into the detents on the posts Insert a round shanked tool such as an awl behind the spring and push the tool in bending the wire toward the hole center nee ics Overbending can either break the spring and or not allow the post to be reinstalled Test the operation of the head restraint after installation to assure it s not too tight a oa RS Thanks to Fred Tebbet and Wayne Zigler Ordering Replacement PCMs for 2001 Trackers Both
3. s a towing pop quiz Answers are at the end of the article 1 Do you know why the ignition must be OFF when towing a 2001 Oldsmobile Alero 2 Do you have to use a flat bed carri er on a Corvette 3 You will find recovery hooks on which of the following Cadillacs DeVille Eldorado Catera Seville 4 When attaching a Chevrolet M alibu to acamier where on the suspension do you attach the J hooks 5 Is it permissible to use a sling to pick up the front end of a Pontiac Firebird Questions like these must be faced every day by tow truck operators who bring disabled vehicles to your dealership for service And many of them will look to you as experts on the correct way to lift and tow the vehicles your dealership services Every year GM updates and publishes and pictures the equip ment required to per form the towing proce dures outlined in the book These include auxiliary load spreaders fabricated of wood Safety chains lift chains T and R hooks and towing dolly The manual describes the location and purposes of recov ery hooks incorporated on numerous new vehi cles and points out that they are not sub stitutes for securing the vehicle to a carrier There is also a sec tion dealing with restraint systems including air bags and the proper handling of deployed inflator modules These manuals are distributed by Helm Inc Publication Division 14310 Hamilton Avenue High
4. spark knock in the Duramax The scenario would be a complaint of a Spark knock during normal driving conditions other than the Slight knock heard during shifting which is normal Drive the vehicle and attempt to repeat the complaint Once the spark knock begins to occur take your foot off the accel erator shift the vehicle into neutral and take a snap shot using the Tech 2 This will allow the vehicle to enable Cylinder Balancing Rates during your drive Observe these rates and note which cylinder s appear higher compared with the other cylin ders The cylinder s with the higher than normal rates will indi cate the injectors that are slightly sticking either open or closed during the driving condition in which the complaint occurs The Injector s may not show an abnormal balancing rate at idle Once you verify the complaint and then perform the driving test determine if the balancing rates are higher than normal Vacuum Pressure Gauge The vacuum pressure gauge is alSo useful when diagnosing the Duramax 6 6L diesel In the case of a complaint of starts runs then dies or if the vehicle will not start after sitting for a period of 30 minutes or longer hook up the vacuum pressure gauge to the schraeder valve on the nght front valve cover to i determine if air intrusion into the fuel system is the root cause of the complaint With the vacuum pressure gage hooked up prime the fuel manager until 10 ps
5. The diameter of the Multec 2 is about 1 2 that of the Multec 1 and it is also lighter Although the Multec 2 has a quicker opening response the stroke of the core is twice the length of the continued on page 3 CORE SPRING M ultec Se tate a Se 5 i Se Testing the Multec 2 Fuel Injector How to Find Control Module References in SI2000 1 Obtaining Broadcast Codes Transmission Shift Conditions Tech Tips Exhaust Rattle at Idle Sulfur Smell from Exhaust Painted Axles on Camaro and Firebird Tracker PCM Can Be Reprogrammed Head Restraint Migrates to Up Position Uncommanded Shift to Auto 4W D GM Towing Manual Duramax Diesel 6 6L Diagnostic Tips TAC Tips Rough Idle Aztek and Rendezvous Trailering Package Ambient Temperature too High GM Goodwrench Remanufactured Engines Bulletins cM Service Operations Transmission Shift Conditions No Forward Delayed Forward Transmission may Lock Up in Reverse Intermittent Affects 2000 2001 models equipped with the 4T65E Transmission RPO M15 MN3 MN7 Vehicles with the subject condition will exhibit no forward or delayed for ward intermittently Some will not move intermittently when placed in reverse Putting the vehicle in drive and then back into reverse may allevi ate the condition temporarily This phe nomenon has been observed in only a very small number of vehicles in the field The cause is asmall nick on the forward band piston app
6. a n n n n a TETETELELELEL npa n a m a n n n a n a mn n a n a n n n a n a n a n a n a n a m a n a n a n a n a n a n a n a n a n a n a n a n a nu u u m n ee ee O E Aas ee er na n nea mia eie oja sie aa a asa rA m asa ua nna nnu moa eee ee oe ana ata nta nna ata n i n n n n n n n n n n a ee OOo nnmnnn nnn CETELE n on ETETETT DEET oma BRU R CPT TELELE UELEDI July 2001 Volume 3 No 7 Techline News How to Find Control Module References in S12000 It s often helpful to know exactly what control modules are installed on the vehicle you re servicing Here s a quick way to find a list Go to SI2000 Build the vehicle Select View Service M anual In the keyword search box type control module references This will bring up a table of every module available on the specified vehi cle The modules are listed in the left column Other column headings are Repair Instructions Diagnostic System Check Schematics Within each table box there are hot links to the highlighted information Although this is a helpful directory you should not ignore good diagnostic practice Follow the diagnostic proce dures provided and replace compo nents only when instructed to do so Thanks to Mark Stesney Obtaining Broadcast Codes There are various ways to identify the standard and optional equipment on a vehicle In this example we ll assume you have a 2002 GMC Envoy with a 4 spe
7. BRAKES 01 05 23 006 Revised Fastener Requirements for Front and Rear Brake Caliper Bracket Replacement various Car and Minivan M odels ENGINE PROPULSION SYSTEM 01 06 01 015 Serpentine Belt Frayed Replace Power Steering Pump Bracket and Serpentine Belt 1999 2001 Chevrolet Tracker with 2 0L Engine VIN C RPO L34 01 06 02 003 Rust in Coolant System Heater Inoperative Blows Cold Air Flush Coolant System 1996 Buick Roadmaster Cadillac Fleetwood Chevrolet Caprice Impala SS with 4 3L or oe V8 Engine VINs W P RPOs L99 LT1 01 06 04 023A replaces 01 06 04 023 Revised Fuel Gage Inaccurate or Inoperative Diagnostic Procedure 1999 Chevrolet Malibu Oldsmobile Cutlass 01 06 04 030 Inaccurate Fuel Gauge Reading Reprogram PCM 2001 Chevrolet and GMC G Van Models with 35 Gallon Fuel Tank RPO NL1 Built Prior to October 2000 TRANSMISSION TRANSAXLE 01 07 29 003A Transmission J umps Out of Gear Replace 3 4 Shift Fork 3 4 Synchronizer Assembly 3rd Gear Blocker Ring and 3rd Speed Gear 1999 2000 Chevrolet Camaro Pontiac Firebird with M anual Transmission RPO MM6 01 07 30 002B replaces 01 07 30 002 Malfunction Indicator Lamp MIL On Transmission Stuck in Third Gear Instrument Cluster Inoperative Replace Ignition Switch various Utility models with 4L60E or 4L65E Automatic Transmission RPOs M30 M32 01 07 30 018 Tech 2 Information on 4L60E Shift Adapts Clearing Shift Adapts
8. Delphi also recommends using the injector noid light J 34730 405 When plugged into the connector in place of the injectors the noid light permits you to verify that power is supplied to the injector and that the injector driver is functioning Thanks to Randy Pearl Using J 34730 405 noid light ad es eed hoe eed ee a Gey oi d uf a Do ee es ee e E lt hme assembly and modules ABS convenient way Component Code GM Vehicle Inquiry System others oe Of course you can always check the broadcast code directly on the component but that can entail putting the vehicle on a lift using an Inspection light and mirror you know the drill Now there s a more Hooper am Cee Hieber bek Beth etry Sorgen irene aea Eh alee itor Career code include engines transmis sions and transfer cases axles ECM PCMs and other control On the Dealer World home page http www gmdealerw orld com choose Service choose GMVIS On the GM Vehicle Inquiry System page type in the last 8 digits of the VIN and submit choose Vehicle Component in the page header This will bring up a Vehicle Component list For each com ponent you will see Source Plant Broadcast Code Traceability Number TIP Use the HELP key to obtain a definition of these terms Your parts departmen
9. 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 continued from page 7 Multec 1 for improved resis cuca tance to contami pmc nation and reduced Sensitivity to inter nal wear The improved fuel flow path cre ates smaller spray particles and increased spray velocity and also minimizes contami nation traps To guard against corrosion stainless steel is widely used for internal compo nents including the director plate which has precision holes to control fuel flow and spray targeting
10. production and service replace ment PCMs are available for order Do not order a PCM with a part number that begins with 3002 These are production PCMs and are often damaged when recalibration is attempted Correct PCMs are available for the US market using the following part numbers and applications 2 0 L man trans 4 dr 91176340 2 0 L auto trans 4 dr 91176341 2 0 L man trans 2 dr 91176342 2 0 L auto trans 2 dr 91176343 2 5 L auto trans 4 dr 91176346 Trackers built for sale in Canada or M exico should use the following part numbers and applications 1 6 L man trans 2 dr Can 91176338 1 6 L man trans 2 dr Mex 91176339 2 0 L man trans 2 and 4 dr Mex 91176344 2 0 L auto trans 2 and 4 dr Mex 91176345 Thanks to Donald B Sherman Avoiding Door Trim Cracks On 2000 01 Chevrolet Impala front door trim panels may be cracked or broken on the forward or rear edge of the panel These cracks are typically in line with the door trim mounting bracket screws To avoid this damage before attempting to remove the trim panel remove the two attaching screws located behind the armrest pull cup Then disen gage the trim panel retainers from the door inner panel using J 38778 Discard the trim panel retainers and replace with new ones when installing the door trim Thanks to Gary M cAdam Tracker Hydraulic Valve Lifter Noise Some 1999 2001 Chevrolet Trackers with 2 0 and 2 5 liter engines have h
11. 1 02 Pontiac Aztek 01 08 56 001 Security Lamp Illuminated on IP Engine Stalls No Start DTC B2960 Security System Sensor Data Incorrect but Valid Set Inspect and Repair Cause of DTC B2960 1998 2001 Chevrolet and GMC S T Pickup and Utility Models Oldsmobile Bravada 01 08 52 002 Programming Remote Keyless Entry RKE Transmitters 2001 Chevrolet M alibu Oldsmobile Alero Pontiac Grand Am 01 08 56 002 Security Lamp Illuminated on IP Engine Stalls No Start DTC B2960 Security System Sensor Data Incorrect but Valid Set Inspect and Repair Cause of DTC B2960 1999 2001 Chevrolet and GMC C K Pickup and Utility Models 01 08 56 003 Security Lamp Illuminated on IP Engine Stalls No Start DTC B2960 Secunty System Sensor Data Incorrect but Valid Set Inspect and Repair Cause of DTC B2960 1999 2001 Chevrolet and GMC M L Van Models 01 08 58 002 General Windnoise Water Leak Diagnostic Guide 1998 2001 Chevrolet Camaro 1998 2000 Pontiac Firebird 01 08 63 003 Hood Will Not Latch Reroute Hood Release Cable 1997 2001 Chevrolet Malibu 1997 1999 Oldsmobile Cutlass 01 08 66 004 TrapAlert System 2001 Chevrolet Impala Monte Carlo RESTRAINTS 01 09 41 004 Air Bag Indicator Illuminates Intermittently Side Impact Air Bag Module DTCs B0029 or B0041 Set Replace Driver or Passenger Side Impact Air Bag Module 2001 Chevrolet Venture Oldsmobile Silhouette Pontiac Aztek Montana Uncommanded Shift t
12. 2002 Chevrolet TrailBlazer GMC Envoy Oldsmobile Bravada with 4L60E Automatic Transmission RPO M 30 and 4 2L Engine VIN S RPO LL8 01 07 30 020 4L60E Valve Body Spacer Plate and Gasket Kit Ordering Reference Table 1998 2001 Chevrolet Camaro Corvette Pontiac Firebird 1999 2001 Chevrolet and GMC C K Trucks with 4L60E Automatic Transmission RPOs M30 M32 01 07 30 021 replaces 83 71 10A Park Neutral Position Switch Connector Cannot Be Removed Replace Switch and Connectors various Passenger Car and Light Duty Truck Models with 4L60E M30 4L65E M32 4L80E MT1 or Allison LCT M 74 Automatic Transmission BODY AND ACCESSORIES 00 08 61 001B replaces 00 08 61 001A Revised Assist Step Installation Procedure 2000 01 Chevrolet and GMC Utility Models 2002 Cadillac Escalade 00 08 49 006 Erratic Instrument Panel Indicators Gauges Needles Pointers When Vehicle Ignition is Switched On Reprogram Instrument Panel Cluster Software 2002 Chevrolet and GMC S T Utility Models and Oldsmobile Bravada New Style 01 08 44 006 Clearing CLN Message from Audio System After Cleaning the Cassette Tape Player 2001 Chevrolet and GMC C K Utility Models with Cassette Tape Player RPO UPO 01 08 46 001 Required Reconfiguration of OnStar Modules After Replacement All 2000 01 Passenger Cars and Trucks with OnStar 01 08 49 0007 Instrument Panel Carrier Cross Vehicle Beam Bolt Removal 2002 Buick Rendezvous 200
13. ed automatic transmission in your service bay How would you describe the transmission The model of the transmission is the 4L60E which is also known as RPO M30 But if you go to the parts depart ment to obtain parts for that transmis Sion they will want to know the broad cast code This is a number which is related to the specific calibrations or running changes in the transmission During the production year there may have been a change in a spring calibra tion or a valve for instance which would result in a different broadcast code Components that have a broadcast continued on page 3 n t le ne a CORE ee In the J anuary 2001 issue of TechLink we covered the subject of fuel injector testing Here s some addi tional information which pertains to the Multec 2 injector Comparison of Multec 1 and Multec 2 Injectors The onginal Multec 1 injector was used from 1985 through 1999 In this injector design the electrical coil was exposed to the fuel that passed through the injector The fuel acted as a coolant for the coil Some high alcohol content fuels and cleaners could erode the insulation on the coils leading to a failure To address the condition the Multec 2 injector was introduced in 1999 Its design is much different from the Multec 1 in that the intemal coil is Separated from the fuel that is passing through the injector This eliminates coil Shorting due to insulation erosion
14. est electrical test for the Multec 2 is the resistance test using an ohmmeter To do this disconnect the electrical connector from the Multec 2 and inspect the terminal pins If they are Satisfactory connect your digital ohm meter across the injector using suitable test terminal adaptors A satisfactory reading is 11 to 13 5 ohms at room temperature The reading will increase as the temperature rises If measure ments are taken with engine coolant temperature above 100 F or below 50 F the best bet is to read all the injectors and com pare readings looking for sig nificant variations Normal injectors should be within 1 5 ohms of each other If the resistance is low in the 4 5 ohm range an internal short is indicated Opening response time will be affected Also there s a likelihood of excess heat being generated in the continued from page 7 shorted area If the resistance is high 60 70 ohms the coil cannot create enough magnetism and the injector may not open TIP If all injector readings are satis factory and the engine now runs prop erly after checking resistances the cause of a misfire may have been a poor connection at one or more injec tors which cleared up simply by discon necting and reconnecting Other Tests The J 39021 Fuel Injector Tester can be used to perform an injector balance test See SI2000 for details Be sure to set the selector switch to the 0 5 2 5 amp setting
15. ezvous For a 2001 vehicle you must verify that it has the early cam profile by read ing the 3 alpha characters of the broad cast code listed on the tag attached to the engine s rear cam cover The broadcast codes for early 2001 engines are Seville DeVille applications Engine VIN Code Y KMA Engine VIN Code 9 KKA Eldorado applications Engine VIN Code Y KCA Engine VIN Code 9 KBA Aurora application Engine VIN Code C KY A Once all four camshafts have been installed the calibration must be updat ed Contact Techline and tell them that the camshafts on the vehicle have been replaced Techline will provide a VCI num ber to install the correct calibration Techline must be contacted each time so that they have a record of when a camshaft change occurred on each vehi cle This will ensure that future calibra tions for that vehicle will be correct GM Technical Assistance Ambient Temperature Reading Too High Owners of some 2001 Chevrolet Silverado or GMC Sierra trucks may comment that the ambient tempera ture reading in the rearview mirror is too high when the winter front is installed over the radiator grille to restrict air flow into the radiator and increase engine temperature The sen sor is reading the engine compart ment temperature instead of the ambient temperature due to its loca tion Reposition the ambient tempera ture sensor to an existing hole on the radiator support under the left turn s
16. i is reached If pressure does not reach 10 psi after twenty or so pumps air intrusion is the cause Refer to the fuel system diagnostic in the manual In the case of a cranks no start condition use the Tech 2 to check for codes If no codes are present ensure that pres Sure iS being made under Engine Data 1 looking at Actual Fuel Pressure If pressure is being made install the vacuum pressure gage follow the cranks no start diagnostic and then prime the fuel manager until 10 psi is reached If the 10 psi leaks down to zero faster than the specified time within the fuel system diagnostic the problem could be internal to the high pressure pump Observe the fuel system diagnostic and follow the guidelines provided in order to determine if the pump is the problem Thanks to Christopher Sterling Sulfur Smell from Exhaust Owners of some 2001 Chevrolet Trackers may comment about a sulfur smell from the exhaust particularly when the vehicle has less than 800 miles The sulfur smell is a normal operating characteristic result ing from the highly efficient catalyst within the new coverter As the catalyst ages through continued vehicle operation the sulfur smell will diminish Although the exact mileage cannot be pinpointed the smell should be significantly reduced in the first 2000 miles Do not change the catalytic converter in response to customer com ments regarding the sulfur smell because it will not el
17. ig nal assembly This hole is exactly opposite the location used to install the air temperature sensor under the right turn signal assembly Relocating the sensor will elimi nate the bracket in the original loca tion The wiring hamess will now be 12 inches 304 8 mm longer than needed Neatly bundle the excess wire and install a suitable tie Affected Models 2001 Chevrolet Silverado C2 C3 2001 Chevrolet Silverado K2 K3 2001 GMC sierra C2 C3 2001 GMC sierra K2 K3 GM Technical Assistance Significant Quality i acidic in GM Goodwrench Remanufactured Engines GM SPO changed suppliers for the 4 3L L35 LB4 LF6 GM Goodwrench engine assemblies during 1999 and has instituted several quality improvement items during this change over The cut off date for the latest of all improvements was December 1999 Bulletin 00 06 01 019 has been released ii to help identify and resolve oil consumption concerns of the 4 3L remanufac tured engines To aid in the process of continuous improvement for this engine series you are asked to provide the Serial number 8 digit number and the engine build date sequence number informa tion on the Repair Order in the event you need to replace a 4 3L GM Goodwrench engine This information can be read from the engine ID tag GM Technical Assistance includes the following items but does not include a hitch platform self leveling rear suspension G67 auto level control com
18. iminate the smell Installation of a new converter prolongs the duration of the smell because it starts the process over again Thanks to Donald B Sherman Painted Axles on Camaro and Firebird The St Therese Assembly Plant will install painted rear axles from about Aprl 4 to the week of May 14 2001 for engi neering evaluation only Painted axles will not be standard production so unpainted axles should not be painted in the field Thanks to Mike Ondre Return to page 1 Chevrolet Tracker PCM Can Be Reprogrammed For a number of years the PCM in the Chevrolet Tracker could not be repro grammed and had to be replaced if a cal libration change was needed But effec tive December 1999 that is no longer true The Tracker PCM for model years 1999 and newer can now be repro grammed as explained in bulletin 99 06 04 060 Two Examples where Reprogramming is the Correct Solution Rough Unstable Idle During Engine Wam Up Bulletin 00 06 04 013 issued in March 2000 addresses a rough idle condition on 1999 2000 Trackers with manual transmission Customers may comment that the vehicle runs rough when idling with the clutch depressed after a cold start before the coolant reaches nor mal operating temperature The actu al idle soeed may drop below the desired speed Reprogramming the PCM is the proper correction for this condition Tach Needle Fluctuation On 2001 Trackers with 2 5L V 6 engine and auto
19. land Park MI 48203 phone fax 800 551 4123 313 865 5927 web address www helminc com 1995 1997 1998 1999 2000 2001 T66 T67 GM PT98TOW GM PT99TOW GM PTOOTOW GM PTOLTOW Thanks to Mike Ondre the GM Passenger Car and Light Duty Truck Se Towing M anual with all ee these answers and more Although your dealership an et received one copy you may want to obtain addi tional ones for handy ref erence An important feature of the manual each year is the What s New sec tion Here for 2001 you ll find information on avoiding battery run down while towing dealing with remote keyless entry and content fi theft features The manual describes Front and rear hookups are shown for every vehicle Return to page 1 Duramax Diesel 6 6L Diagnostic Here are some diagnostic tips you may find useful when diagnosing driveability concems on the Duramax 6 6L diesel engine Misfire If there is a misfire code or a misfire can be detected during operation connect the Tech 2 Look on the Engine Data 2 list to find the Balancing Rates for the cylinders Balancing Rates This will show the amount of fuel being added to or taken away from each cylinder during normal idling Normal_fuel deliv ery to each cylinder is around 1 cubic millimeter mm3 for the pilot injection and 7 mm3 for the main injection Balancing rates are available only during idle These numbers tell y
20. ly pin 21 that causes the apply pin to stick Even though the nick may be quite small no larger than the tip of a sharpened pencil it may still be sufficient in size to cause the pin to Stick Replace the pin and any associated parts that are required to correct the condition Thanks to Chris Anderson Slips Erratic Shift Harsh Shift Affects 2001 Cadillac DeVille Eldorado and Seville 2001 Aurora equipped with 4T80 E RPO MH1 It is possible for the subject condition to be caused by a faulty crank sensor Premium V8s use two crank sensors allowing for significant redundancy should one sensor fail two sensors allow faster synchronization one sensor alone can pro vide approximately 90 functionality If a crank sensor failure occurs the powertrain operation is severely degraded until the diagnostic code s are set This mode of operation could be interpreted as the transmission slipping or shifting erratically When a crank sensor code sets while the car is being driven it causes a momentary loss of engine output during transition to the other sensor This may be interpreted as a very firm shift So if a technician is servicing a vehicle with the subject condition it is important to address any DTCs associated with the crank sensor first P0335 P0336 P0385 P0386 etc Thanks to Chris Anderson No 2nd or 4th Gear Some 4L60E transmissions in 2001 vehicles may experience a damaged 2 4 band with no obvious root cau
21. o Auto 4WD On 2002 TrailBlazer and Envoy if the transfer case selector switch on the instrument panel is placed in a position between the 4HI and 4LO positions the transfer case will shift into the Auto 4WD mode Turning the knob to various positions changes the electrical resistance through the switch When the switch is between the 4HI and 4LO positions the resistance is within the specifications for the Auto 4WD mode This leads the transfer case control module to read the switch position as a request for Auto 4WD mode This condition cannot be repaired All switches will have the same result If this occurs instruct the operator to place the switch in the detent in the desired position This issue will not occur if the switch is in the proper location with the selector pointing at the indicator light for 4LO or 4HI Thanks to BJ Lackey Return to page 1
22. ou whether or not you have a possible compression prob lem or possibly an injector that is stuck open or closed Once the misfire is detected the balancing rate of the cylin der that has the miss will be slightly higher in mm or may be as high as 12 mm The misfire codes P0300s will set only in the first 90 seconds of engine operation and will set only when the balancing rate of the missing cylinder goes above 7 mm The normal values that should be seen on the balancing rate screen will range between 2 4 and 2 4 These numbers will move around constantly based on the crankshaft speed Suspect a possible problem when the balancing rate of a particu lar cylinder starts to go up in mm An example of a possinie problem cylinder would be a balancing rate of 5 mm or so Once the numbers start to creep up the cylinder is progressive ly getting worse in performance Once the balancing rate has been determined to be higher than normal follow the Smoke Table Diagnostic White Smoke Remove the glow plugs from the side of the engine that has the cylinder with the higher than normal balancing rate Remove the ignition 1 relay to disable the injectors Then crank the engine and have someone observe the glow plug holes from a dis tance for safety reasons The glow plug hole that has fuel Spraying from it is the cylinder with the stuck open injector Diagnosing Spark Knock Balancing rates are also useful when diagnosing
23. pressor outlet for blowing up balls bike tires etc engine oil cooler high output alternator 125 amp heavy duty engine cooling system wiring hamess The frame mounted hitch platform is now available from GM SPO FWD Aztek only 12497335 AWD Aztek amp all Rendezvous 12497875 3 2 The maximum trailering capacity for these vehicles is 3 500 lbs which falls into the Class II category Tongue load Information is not available VENDOR NUMBER AS ASSIGNED GM Technical Assistance capella pete AREA Return to page 1 June 2001 This review of service bulletins released through mid une lists the bulletin number Superseded bulletin number if applicable Subject and models GENERAL INFORMATION 01 00 89 008 replaces 96000 Current CIPS Campaign Number to Previous Divisional Campaign Number 2002 and Prior Passenger Cars and Trucks 01 00 89 009 Replacement of Keys Key Numbers and or Security Chips 2002 and Prior Passenger Cars and Trucks HVAC 99 01 39 004A replaces 99 01 39 004 Air Conditioning Odor Install Kit 1993 2002 Passenger Cars Light amp Medium Duty Trucks 01 01 38 006 Air Conditioning System Flushing Procedures and Guidelines 1997 2002 Passenger Cars and Light Duty Trucks with Air Conditioning SUSPENSION 00 03 10 003B replaces 00 03 10 003A GM Tire and Warranty for Bumper to Bumper Program 1996 2001 Passenger Cars and Light Duty Trucks
24. se One possible cause of this condition may be a servo apply pin that does not move freely in its bore causing the 2 4 band to drag when released During transmission assembly a gauge is used to determine proper servo apply pin length If the gauge strikes the case near the apply pin bore it is possible to dent the case This dent may raise metal in the bore and cause the pin to drag Inspect the case inside the servo bore for signs of a dent or damage near the apply pin bore Also inspect the apply pin for scratches or wear marks running length wise along the pin If damage is noted it may be possible to carefully remove the raised metal with a small file If the raised metal cannot be removed it will be neces sary to replace the case or the transmission assembly based on the most cost effec tive repair Thanks to Mike J ohnston 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 Manager Marie Meredith Desktop Publishing Greg Szpaichler MediaW urks lt Spake mediawurks com FAX number 1 248 649 5465 Write to D
25. t will be able to use this information to help obtain the correct parts for your repair Thanks to Glona Rogers Return to page 1 Exhaust Rattle at Idle Some M L vans trucks between 1996 and 2001 with L35 4 3L engine may exhibit an exhaust rattle noise The noise is most likely very harsh occurring near idle at 550 RPM In some cases engaging the AC com pressor may increase the rattle The noise is most likely to occur in warm ambient temperatures with a hot exhaust system The exhaust tailpipe will be visibly vibrating and the rear 1 3 of the muffler will be oil canning while the noise is occurring Applying pressure to the tailpipe will reduce or completely eliminate the noise The condition may be caused by low clamp load on the exhaust seal at the takedown This can be con firmed by applying pressure to the joint with a screwdriver while the noise is occurring If the problem is in the joint pressure will eliminate the noise There are three standoffs on each exhaust flange bolted to the exhaust manifold If any two of the standoffs on one flange is in contact with the manifold during a hot exhaust condition the noise can occur To correct this condition lower the exhaust Y pipe Measure the height of the standoffs on the flanges Remove 2mm from all 6 standoffs Install new seals Place the Y pipe into position Torque uni formly to 53 3 Nm Thanks to Marty Case GM Towing M anual Here
26. ydraulic valve lifter noise upon engine startup The hydraulic valve lifter design may allow the oil to drain down Air may get trapped in the valve lifters not allowing for proper lifter adjustment The valve lifter clatter can be heard until the air is eventually replaced by engine oil GM Service Bulletin num ber 00 06 01 006A recommends purging the air by running the engine at 2000 RPM for about half an hour or until the air clears Thanks to Donald B Sherman Return to page 1 TAC Rough Idle Some 2000 and early built 2001 model year Cadillac DeVille Eldorado Seville with 4 6L LD8 L37 engines or 2001 Oldsmobile Aurora with 4 0L L47 engine may exhibit a condition of rough idle with no PCM DTC and no driveability complaints A technical bulletin is expected to be released soon explaining that a camshaft and PCM calibration may be required The camshafts must be replaced on all 2000 vehicles with 4 6L LD8 or L37 engines and the early built 2001 vehicles with 4 0L L47 or 4 6L LD8 or L37 engines 4 6L LD8 VIN Code Y and 4 0L L47 VIN Code C camshaft service part numbers 12570333 RH INT 12570331 RH EXH 12570332 LH INT 12570334 LH EXH 4 6L L37 VIN Code 9 camshaft service part numbers 12570335 RH INT 12570337 RH EXH 12570336 LH INT 12570338 LH EXH Aztek and Rendezvous Trailering Package The High Performance trailering package RPO V92 available on FWD amp AWD Aztek and Rend

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