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The 6.5L FAQ's... The Master List of Information and 6.5 Answers

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2M views 16 replies 5 participants last post by  Freddyack 
#1 · (Edited by Moderator)
Here is a compiled listing of the most popular 6.5L topics discussed here at DieselPlace.com. This is to help you speedily find your answers, without having to wait for a reply to your question. We love to answer questions, and enjoy gathering around the computer to help others out. We’ve all been there. This forum is a living library of information.

Click on the solid underlined word of any topic of interest and it will hyperlink you to the area in the forum where the information was first posted.

If you don’t find a topic listed, feel free to do a search. You may have to do an individual word or a phrase search, as with any search engine you may need to be creative in describing what you are looking for, don't give up if the first search you type comes back with nothing found. There is an entire forum search, and you can search within a forum sub group, author, subject or date. It may be worth your while to read all FAQ topics first so you can inject common phrases to work with on your searches.

Best way to use this thread:
Hit Control + F and depending on your browser, a "Find" box should appear. Type in a main word (example: injector) and hit enter or next. This will search the thread and highlight every time the word "injector" comes up. Or, you can just browse around the thread and find what you need. Everything is in alphabetical order.

Building the FAQ library - If you see a topic that you want to add or think should be added, please paste a link in a PM to a staff member. Or, click the Report Button - include a blurb in the report indicating you would like to submit the thread for inclusion in the FAQ.

Latest updates posted February 2024

Thanks and enjoy!
The Diesel Place Staff
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FAQ Contents


A Through E Click Here


F Through H Click Here


I Through O Click Here


P Through S Click Here


T Through Z Click Here

* 6.5 NEWBIES * Click Here

1992-1993 C/K Truck Reference Information Contains Student Handbook and TSBs Click Here

1994-1999 C/K Truck Manuals Click Here

OBDI & OBDII Code Summaries and Diagnostic Manuals: Click Here

Parts List: Click Here

Do It Yourself (DIY) Articles: Click Here

Technical Services Bulletins and Wiring Diagrams - Search for TSBs and Wiring Diagrams for all model year trucks Click Here

Rolling Coal and the 6.5L: Click Here

6.5 Diesel Photo Thread: Click Here

FAQ: Purchasing 6.5L Diesel: Click Here

6.5L Diagnostic Check List Click Here

Fun Threads

Other Topics
 
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#2 · (Edited by Moderator)
C/K Truck Manuals

6.5L C/K Truck Manuals
:

1994 C/K Truck Manual Click Here

1995 C/K Truck Manual Click Here

1996 C/K Truck Manual Click Here

1997 C/K Truck Manual Click Here

1998 C/K Truck Manual Click Here

1999 C/K Truck Manual Click Here

Thanks to Glagulator for the C/K truck manuals

Stanadyne Reference Manuals and Service Bulletins
:

Stanadyne Operating and Instruction Manual Model DB2 Pump Click Here

Stanadyne Model DS Electronic Fuel Injection Pump Operating and Instruction Manual Click Here

Stanadyne Model DE Electronically Controlled Diesel Fuel Injection Pump Operating and Instruction Manual Click Here

Oregon Fuel Injection Inc - Stanadyne Pump Diagnostic Troubleshooting Click Here

Stanadyne Service Bulletins

SB 438R10: Click Here

SB 500R2: Click Here
SB 561R1 (ULSD components): Click Here
SB 102R12 Rebuild Parts: Click Here
SB 108R12 DB2 Shutoff Solenoid Service Procedures: Click Here

Other Reference Manuals:

6.5L Turbo Diesel GM Students Handbooks:

*1991 6.5L Student Handbook Click Here

*1994 6.5L Electronic Injection Student Handbook Supplement Click Here

Miscellaneous Manuals:

ASE 8 - Engine Performance Module 16 - 6.5 EFI Diesel Here

Tech Tips Special Edition GM Vehicle Computer Relearn Procedures Here

GM Computer Relearn Procedures Here







.
 

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#3 · (Edited by Moderator)
FAQ A - E

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#18:1 compression EngineTechnical Discussion on the 18:1 Engine
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A

Adding Personal Signature To Posts Here


A1 Customs - A vendor to be very careful of. Aka, steaksauce.
Antilock Braking System (ABS) - Electronically controlled system that senses wheel lockup during braking and relieves hydraulic pressure at wheel which is about to skid.

Acetone - Do not use in your tank!! It easily evaporates at 70deg.

Acronyms- Find out meanings to common acronyms.

Additive(s) - Anything added to crankcase or fuel tank to enhance and preserve operation of the engine system. Additional information available in Fuel Additives

Air Filter Study
- Comprehensive study of various air filters
Air In Fuel System -
  • Symptoms of Air In Fuel System: Click Here.
  • Where Are The Likely Locations For Air Leaks: Click Here.
  • How to Test For Air In Fuel System: Click Here.
  • Picture of Clear Return Line Installed: Click Here.
  • How to Find Air Leaks: Click Here
  • How to Pressurize the Fuel System To Check For Air Leaks: Click Here
Air Intakes - see Boost and Filters

Air Conditioning - To understand this system Click Here.

Alternator - Device that generates voltage which provides power to charge batteries and other electrical devices within the vehicle electrical system.
  • Common problems of a bad alternator - Low voltage, batteries not charging, erratic tachometer readings.
  • Alternator upgrade info in DIY section
  • 1996 & 1999 Alternator pulley size = 2-3/8" O.D.: Click Here
  • 1995 Alternator pulley size = 2-5/8" O.D.: Click Here
  • 1994 Alternator pulley size = 2-5/8" O.D. GM spec: Click Here
Alternative Fuel - Any fuel that is not Diesel. SVO, WVO, Bio-Diesel

APP (Accelerator Position Potentiometer) - This acts as a throttle cable through the drive-by-wire system. Commonly known as an APPS (Accelerator Pedal Position Sensor). Failure modes for the APP system are as follows:
  • If only one sensor fails, the vehicle will operate normally. The PCM will store a DTC, but will not illuminate the “Service Throttle Soon” lamp in the instrument cluster.
  • If two sensors fail, the engine will operate at reduced power. The PCM will store a DTC and will illuminate the “Service Throttle Soon” lamp.
  • If all three sensors fail, the PCM will store a DTC and illuminate the “Service Throttle Soon” lamp. The PCM will also reduce engine power to idle.
  • How to tell when it's bad. Click Here
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B


Battery connections - Various problems associated with these. Read this thread, can cause voltage issues, intermittent stalling, studdering, etc.

Battery Manufacturers - Link to a list in this post Here

Battery Terminals - The stock side terminal connections are weak. You can make your battery connections MUCH more stable by doing a simple mod if you want to keep your side terminals.

Black Smoke & GM 6.5 Turbo Diesel INFO - A topic that regularly rears is head here in the 6.5TD forum is “How can I make my 6.5 smoke like crazy?”, or alternately “My 6.5 is pouring out black smoke, how can I make it stop!” For more information Click Here

Block Heater

Blower Motor -
  • How To Test The Blower Motor: Click Here.
  • How To Remove The Blower Motor: Click Here.
  • Adding Ground To Blower Motor: Click Here.
  • How To Replace The Blower Motor Speed Control aka Resistor:Click Here.

Boost Diagnostics - For information regarding this topic see this thread.

Boost Fooler - By using a 10k Pot you can fool the PCM by adjusting what it reads from the MAP Sensor. For more information about this mod Click Here.

Brakes - Device used to slow or stop a vehicle.
Brochures - GM Sales Brochures, Commercials & Promo's .

.............. 1992 ............. 1993 ............. 1994 ............. 1995 ............. 1996 ............. 1997 ............. 1998 ............. 1999 ............. 2000 .............

Buying a 6.5L Diesel - Please see Purchasing a 6.5L Diesel.
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C


CDR (Crankcase Depression Regulator) - Similar to a PCV valve on a gas engine. It regulates the amount of vacuum in the engine crankcase to prevent oil leaks. Click here for technical info.

CEL (Check Engine Light) - see MIL

Clutch Troubleshooting - Click here

CODES - There are the two styles of computer "codes" that you will be looking for, Pre 1996 (OBD I) and 1996+ (OBD II).
Computer - see PCM

Connecting Rod Bolts - Talk about upgrade to ARP Studs Click Here

Control Arm Bushings - How to on changing 1 ton bushings Click Here

Coolant System - See Engine Cooling

Coolant Crossover Fitting Leak
: Coolant crossover leak

Cooling Modification - upgrade to a 1997+ cooling system (High output water pump and dual thermostat) with this info. See also engine cooling

CPS (Crankshaft Position Sensor) - PCM reads the CPS module to indicate TDC for each piston, necessary to determine precise timing for the injection pulse. Diagram showing CPS location Here

CPS(Crankshaft Position Sensor) - Removal Tips: Here

Crank Pulley

Cruise Control - sometimes fails with a DTC (engine code/service engine light). Can also not work due to a bad PMD.
  • You can add cruise control to your "non-cruise" truck too, Find out here!
CTS - See ECT

Cylinder Compression
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D


Dash (Bezel) Removal - To remove the Dash Bezel (the piece that goes around steering wheel radio, ac controls, etc) Click Here. That link will also show how to remove the gauge cluster.

Door Repairs - Find out how to complete some door repairs yourself by clicking here.

DTC (Diagnostic Trouble Codes) - see Codes or use the DTC lookup tool

Dyno Runs - Click Here to see members dyno runs.
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E


ECM (Engine Control Module) - The primary computer which controls the internal combustion engine. In the 6.5 Diesel we use a PCM, see PCM.

ECM Fuse Blowing - -
  • 1994-95: Try disconnecting the Fuel Filter Manager Fuel Heater, then replace the fuse. Fuel heater power is delivered through the ECM circuit. Deteriorating Fuel Heater harness shorts causing the fuse to blow. See picture to locate Fuel Heater harness Here
  • 1996+: Here
ECT Sensor(Engine Coolant Temperature Sensor) - Sensor is mounted in the t-stat crossover manifold, gives PCM accurate temperature input for determination of advance and fuel rates. The Resistance changes at different temperatures with this sensor.
  • ECT chart of resistance values Here
  • ECT location picture Here
  • ECT 'Fooling' for better cold starts: Great mod for Command-Start systems! Look here
  • For a modified version, Look here

EGR (Exhaust Gas Recirculation) - An emission device that recirculates exhaust gases from the engine back into the intake and combustion chambers. This lowers combustion temperatures and reduces NOx. The EGR is a vacuum based system. for information on the vacuum system, See Vacuum System & Pump
  • EGR Valves can be found on vin "S" trucks (1500, 2500LD trucks, 6 lug hubs).
  • EGR Solenoid Wiring Click Here
  • Rough Idle or Rough Acceleration Click Here
  • If you would like to remove the EGR system from your truck you must either block off EGR ports in intake or get a vin "F" intake and install. Then you must get computer reprogrammed to erase the EGR system from computer (Heath Diesel or Kennedy Diesel reflashes), or you may receive codes and trigger the CEL.
  • For EGR Removal Click Here
EGT - Exhaust Gas Temperature

Electricity - Understanding how to interpret your meter when working on the lift pump and OPS Click here.

Engine Cooling: For information about thermostats see Thermostats

Engine Disassembly - Excellent write up on how to tear down a 6.5L engine with pictures Click Here and Click Here

E-PROM or EEPROM - A blue type chip found inside of the ECM on 94/95 6.5L Trucks.

Ether and the 6.5 Check Here

Extended Crank Time - See Hard Starting May be associated with an optical sensor failure on the IP, but not all hard starting is IP related. Cold weather, with a lot of grey/whitish smoke on start up maybe glow plug related. See Glow Plugs for more information. Read up also on fuel supply issues: Lift pump, OPS, fuel line leaks, etc.
 

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#4 · (Edited by Moderator)
FAQ F - H

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F

Fan Clutch - This is a fluid clutch that controls the engine fan. it reduces fan noise and increases fuel economy.
Feed the Beast - This is a modification to your filter manager. It will increase the fuel flow though the filter manager.
Fish Biting - (or fishbiting) This is the description for when the engine may "miss" or may not fire properly for a very brief instant. As always, do not rule out fuel supply issues with lift pump, OPS, and take a look at PMD. Remember to do as much diagnostic work to prove out all parts that are at fault.

Flex Plate - flywheel for the 4L80E - How to change a flex plate, step by step. In this thread.

Flex plate bolts

11589040 or 1261968 - 4L80 Torque converter bolt 6 required

14088764 or 3727207 - flexplate to crank bolts 6 required
GM's description - 7/16-20X .70


Fuel Additives - Diesel engines built before 2007 need fuel lubrication as the fuel systems were not designed to run on ULSD (Ultra Low Sulfur Diesel). There are many additive options from which to choose.
  • Cold Weather Additives & Anti Gelling Here.
  • Lubricity Additive Study Here.
  • Two Cycle Motor Oil Here.
Fuel Cap - Can cause excessive vacuum in fuel tank. Excessive vacuum in a Diesel fuel tank is not desirable.
  • General Information Click Here.
  • Picture and description how to modify fuel cap for better venting Click Here

Fuel Contamination -
  • Gasoline: Accidentally forget what you were pumping? Gasoline can be a very damaging ingredient to cause a lot of failures within the total fuel system. Read This Thread for more information.
  • Algae/Microbes: If you see black spots in your fuel filter manager bowl or on the filter, Go To The Link In This Post

Fuel Drain - aka T-Fitting or T-Valve. See "Water In Fuel Drain"

Fuel Filter - How To Bleed Air Here

Fuel Filter Bowl Contamination - IP's are under warranty for 11 years or 120,000 miles. Replacement IP's after that time are subject to the indiviual's warranty policy. If replacing under warranty check This Thread out.

Fuel Filter Manager (FFM)- This item is what is on the top rear part of the engine valley. It houses fuel filter, water in fuel sensor, and fuel heater.


Fuel Filtration - Filtering Diesel fuel is very important. Fuel can be dirty and the injection pump must have clean fuel to last.
  • Fuel Screen - How To Replace Video Click Here
  • To see an auxiliary fuel filter setup Click Here
  • Parts list for pre filter setup Here
  • For info on the stock fuel filter Click Here.
  • To view a filter setup pre-lift pump Click Here.
  • For info on a Secondary Fuel Filter setup Click Here
Fuel Line leaks - See Leaks, fuel (This causes air to enter the fuel system and may create stalling, hard starting, or fishbiting)

Fuel Line Install Tips On How To Remove/Replace Click here

Fuel Line Size (Stock/OEM) -
  • 3/8" ID from tank to lift pump, from lift pump to Fuel Filter Manager
  • 1/4" ID from Fuel Filter Manager to Injection Pump and T-valve drain
  • 5/16" ID for the return line back to fuel tank
  • 3.5mm injector return line

Fuel Tank Sock - The fuel tank sock provides the first level of filtering to the fuel system. When replacing the fuel tank sending unit it is critical to use the correct diesel tank sock. For more information, Click Here

Fuel Temperature Sensor - Mounted internally, PCM monitors IP fuel temps to determine viscosity and fuel rates.

FSD (Fuel Solenoid Driver) - Commonly known as a PMD (Pump Mounted Driver). This device that opens and closes the Fuel Solenoid. See PMD - Pump Mounted Driver

FS or FSOL (Fuel Solenoid) - The PCM-controlled injection pump solenoid valve that opens and closes to provide hi-pressure fuel to each cylinder.

Fuel Shut Off Solenoid - How to "gut" the Fuel Shut Off Solenoid Here

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G

Gauges - Gives information about what the engine is doing so you can monitor boost, EGTs, and transmission temperatures.
Gasoline - A fuel that is never to be used in your diesel engine. Do not add gasoline in your diesel tank!

Glow Plugs - A small pencil-shaped heater, must be needed to start the 6.5L engine. For more information click here.
  • GM TSB on 9G Glow Plugs - Replaced By 11G Glow Plugs in 1996 Click Here
  • GM TSB on 11G Glow Plugs - Replaced in 2000 By "BERU" Glow Plugs Click Here
  • Glow Plug Cycle Time Chart - Based on Temperature and Battery Voltage Click Here
  • Glow Plug Over Ride Modification Look Here
  • Another way to get more glow duration time Convince the PCM that it's -40* out. See how here or here.
  • Swelled Glow Plug Removal: Click Here.
  • Not so common failure of glow plugs Click Here.

Glow Plug System Troubleshooting Tips
  • How to "Read" Glow Plugs: Click Here
  • Glow Plug Relay Connector Voltage: Click Here
  • No Wait To Start Light/Glow Plug Relay Not Working: Click Here
  • Wait To Start Light Comes On While Driving: Click Here
  • OBDI Trouble Shooting Guide Here

GMTDScan Basic - GMTDScanTech - See Scan Tool

Grounds - Proper grounds are very important!
  • Engine Grounds: A complete write up with pics Click Here.
  • Engine Grounds - Another write up with pics in a .pdf file Click Here
  • Alternator Mounting Points: Critical for alternator performance Click Here
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H

Hard Starting - Several reasons given. Search for GLOW PLUGS, Optical sensor, optic sensor, PMD, OPS, lift pump. There are a variety of reasons given for difficulty in starting. Read this thread.

Harmonic Balancer - Rubber-isolated cast-iron ring and hub assembly mounted on the crankshaft nose that is prone to failure. The balancer fails as the rubber deteriorates, and it contributes to crank breakage/failure. See this thread for more information.
  • How To Install Here
  • Removal/Install Tools Here and Here
  • Tool For Stopping Engine Rotation While Removing/Installing Harmonic Balancer Click Here

Heads/Headgasket Issues - to understand better what's happening inside the engine and pin down where the problem maybe, GMCTD explains better the failures here in this post.

Head Lights - There are a few mods you can do to make your head lights work better when driving at night.
  • For one way to do the "All On Headlight Mod" See Here

Heater Hose Tee - Suburban heater hose Tee fitting - DIY fix Here

High Idle Modification - a straightforward and inexpensive Mod you can do yourself to raise the idle rpm of your truck. Comes in 2 easy-to-follow flavours, complete with pictures:
HO Water Pump - '98-up 130gph pump, part of the required coolant upgrades, HO is cast into the upper housing
  • For information about the HO Water Pump Click Here
  • Also refer to Engine Cooling 6.5 Cooling System Upgrade Parts
Hydro-Boost
 

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#5 · (Edited by Moderator)
FAQ I - O

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I


IAT (Intake Air Temperature) - Sensor, mounted in the upper intake plenum, PCM monitors IAT to determine fuel rates and safe levels of Boost

Information, Literature - For some information about literature on the 6.5L diesel Click here.

Ignition Switch - Point of failure that can create stalling. This is NOT THE KEY MECHANISM, but a multiple-circuit switch with relay-type contacts that powers all the components during the "run" state. Upon failure, you will lose dash board and engine will stall - it mimics turning key off. Most folks instantly think that the PMD is at fault, but from time to time, this is actually the cause.

For trouble shooting Ignition Switches:
1994 & 1995 See this thread for details.
1996+ See this thread for details.

For details on removing the key tumbler, see this post with a PDF of the process..

Injection Pump (IP) - The fuel delivery device that pumps high pressure fuel for injection into the cylinder at the precise time for a combustion event in the cylinder. Your pump will vary depending upon model year. 1993 and earlier is a mechanical DB2 pump. 1994 and thereafter is a DS4 electronically-controlled injection system.

  • DS4 IP Component Diagram Here
  • How A Mechanical IP Works Here
  • How To Install A Larger IP Inlet On A DB2 IP Click Here
  • For operation information See Here.
  • Injection Pump/Injector Line Diagram Here
  • DS4 Key Components Picture Click Here
  • DS pump info for lower lubricity fuels See Attachment Here.
  • The injection pump has a 11 year 120,000 mile Extended warranty, for more information Click Here.
  • To turn fuel up on a DB2 pump Click Here For a video of how to do it Click Here
  • Reference thread on different methods to turn pump up Click Here
  • How to Replace Injection Pump? Click Here to see how with Pictures! For another thread about this Click Here and Click Here.
  • Dead Injection Pump, Diagnosing the Pump and CableClick Here.
  • Injection Pump Closure Time Information - DS4: Click Here
  • IP Turning Tool Click Here
  • DTC35 & DTC 36 - If you are getting both codes, here is a diagnostic tip Click Here
  • DS4 IP Diagnostics Click Here
  • DS4 to DB2 conversion: Click here
Injection Pump Service Bulletins
  • GM Service Bulletin - Code DTC 35/DTC P1216 Click Here
  • 6.5 Stanadyne Diagnose Service Bulletin Click Here
Stanadyne Parts Bulletins
Stanadyne IP Application - 6.2L & 6.5L Engines
Injectors Injects diesel fuel into the combustion chambers.
Intake modifications - snorkel mod

Intercooling - Cooling (Boost) charge-air See also WMI or water mist injection
  • Here's a How-To install of a Spearco Intercooler by Turbine Doc
  • Here's a DIY WTA intercooler install: here
  • Here's a DIY hanging ATA intercooler install: here
  • Here's a Step-by-step DIY hanging ATA install: here and here
  • Here's a Top-Mounted DIY ATA install: here and here
  • DIY Water Mist Injection system using mostly off the shelf parts: Click Here
  • Finally, here's a Front-mount DIY install: here
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J

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K


KOKO Procedure - See TDC Offset
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L


Leaks, fuel - Fuel tank and lines as reported by some mid 90's owner's
  • Using Air Pressure To Find Fuel System Leaks: Click Here.
Lift Pump - Small electrical fuel pump that is located on the frame rail under the drivers seat. Noticeable "purring" noise when engine is off. Known trouble spot. This can cause lack of power, hard starting, stalling, etc.

Lift Pump Facts (from GM Service Manual):
  1. The 1988-1993 Model Year lift pump should deliver fuel with a minimum volume of 0.24 liter (1/2 pint) in 15 seconds at a pressure of 40 to 60 kPa (5.8 to 8.7 psi).
  2. The 1994+ Model Year lift pump should deliver fuel with a minimum volume of at least 0.24 liter (1/2 pint) in 15 seconds and pressure of 3 psi minimum with the engine cranking, the ESO disconnected, and the fuel line open after the filter to an approved canister
  3. When the pump is at rest, a spring pushes the hollow plunger in the direction of the outlet. Both the inlet and outlet valves are closed, keeping fuel in the supply line from draining back to the fuel tank.
Lift Pump Trouble Shooting

  • Lift Pump Test & OPS Diagnostics Click Here. See Electricity for troubleshooting practices
  • Pictures showing how to jump the Lift Pump on a 1992-94 6.5L Here
  • Pictures showing how to jump the Lift Pump on a 1995 6.5L Here and Here
  • 1996+ Lift Pump Prime Connector - Apply 12v to this connector to run the lift pump: Here
  • Reference for operating the lift pump with auto tranny in D and key in crank position Here
Lights, LED - Add LED to your gauge cluster for a custom look, Check This Thread for information.

Limp Mode - A Backup Mode of allowing the engine to run, yet not at full power. Usually due to a "missing piece to the puzzle" that the ECM needs to compute timing, fuel delivery, etc.

Locker - Adding a locker? Look at this thread.

Locking up TCC modification to OBD-I trucks. See this thread.

Low Coolant Warning Sensor Location By Model Year See Engine Cooling
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M


Main Bearing Girdle How To Make A 5 Main Girdle Click Here

Manifold Bolt Sizes- Click Here

Manifold Bolt and Heat Shield Part #'s- Click Here

Mass Air Flow Sensor (MAF)-OBDII Trucks
  • Pictures from L56 Here
  • Does your truck have a MAF? Here
MIL (Malfunction Indicator Light) - Also known as Service Engine Soon, Check Engine Light.
  • 1991-1993 With Automatic Transmission - Constant or Intermittent MIL ON, No DTC's Set TSB Click Here
Mirrors - There are different types of mirrors that can be added to our trucks with little to no modification.
  • If you would like to add newer style Chevy mirrors on your pickup Click Here or Or Here.
  • Dodge style mirrors on your truck Click Here.
Missing (Misfire) - Engine briefly "misses" a combustion event. Thread to check out Search for fuel delivery, lift pump, OPS, and PMD.

Modifications (DIY) - Check out this thread for DIY Modifications to your 6.5L Engine and Truck Related Parts!

Motor Mount Inserts Poly Inserts Click Here

Multi Function Switch How to replace the multi function switch in a 1995 to 1998 Click Here
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N

No Start - No Start Checklist: 6.5 Diesel Engine Won't Start? | 6.5L No-Start Diagnostic Guide
No Start Electrical Gremlin Checklist: having issues with TDCO

NV4500 See Transmission - NV4500

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O


OBD (On-Board Diagnostic) - Where PCM monitors all systems, reporting failures with universal numeric codes specific to each system across all OEM vehicle marques.
  • For code explanations see Codes.
Oil - Maintaining your oil is very important in an engine. Make sure you change at the correct intervals and replace with the correct oil. For more information Click here.

Oil Cooler Lines - Stock oil cooler lines are known to leak and cause failures. When an oil cooler line fails, it will lose all the oil and cause an engine failure. Make sure you keep an eye on your stock lines, if they are leaking you are at risk for seizing up your engine.
  • A great alternative to stock lines would be purchasing and installing the Leroy Diesel kit.
  • How To Replace Oil Cooler Lines, With Pictures Click Here
Oil Filters
  • Diagnosing Engine Oil Filters With Collapsed Center Tubes Click Here
Oil Pressure Switch (OPS) - OPS Known trouble spot for not allowing the lift pump to operate. Read this thread. This is also the sensor for the oil pressure gauge in the gauge cluster on dash. When the OPS craps out, your lift pump may not run and the IP can be starved for fuel, leading to stalling, erratic behaviour under load, loss of power, etc.
  • OPS' Role in 1996+ Truck: From Racer55 "For OBDII primary power for the LP is as shown in the diagram, the ECM activates the prime cycle through the relay and once it sees a running engine from OS/CPS signals activates the relay for constant run operation. Should the relay circuit fail, the OPS is backup LP power-it also operates the LP after engine shutdown while oil pressure bleeds off." From glagulator "The lift pump on your 96 gets power from the LP relay and the OPS when the engine is running. PCM control of the LP is independent of OPS function. LP will function normally even if OPS is not. A parallel/redundant circuit. Either source can fail and the other will take over when running. Power for both feeds and the PCM is from the ECM-B fuse, any problem with that and it will not run." Wiring Diagram Here
  • OPS Does Your 1994 - 1995 Truck Need The Relay Mod: Check Here
  • OPS Does Your 1992/93 Truck Need The Relay Mod:Check Here
  • OPS Relay Mod: Check Here.
  • OPS Relay Mod Wiring Diagram: Here.
  • OPS Relay Mod Wiring Diagram - Diesel and WVO: Here
Optical Sensor - The device on the top of the injection pump that provides a high and low resolution frequency signal to the PCM to determine fuel injection timing.
  • How The Optical Sensor Works: Click Here
  • Replacing the Optical Sensor - How To Click Here
  • For 'Optical Sensor Bump' please Look Here for more information.
Optical Sensor Filter Harness - A small device plugs in between the optical sensor and the vehicle wiring harness. The device can cause drive-ability issues if it is not making proper connection. A Picture of the filter harness.

Overheating - See cooling modifications or here.
 

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#6 · (Edited by Moderator)
FAQ P - S

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P

Part Index - listing of parts and part number see this thread

PCM (Powertrain Control Module) - The computer behind your glove box - monitors and controls all aspects of 6.5 electronic fuel injection and 4L80E transmission shifting.
Pictures of things - Photo thread.

PMD - Pump Mounted Driver aka Fuel Solenoid Driver (FSD), Known trouble spot in the 6.5 electronic fuel injection system.

PMD - Resistor
PMD Extension Harness - This is necessary if you want to remote mount your PMD out of the engine bay. Making your own is easy if you are careful. But whether to crimp or solder, that's an ongoing question.PMD - Savanna/Express Van How to get to the IP Mounted PMD Here


Power - We all probably want more power. There are a few options to improve power in your truck. If you don't see anything in this thread try a search, there are many things people have done to their trucks.Power Steering Fluid Flush - How to flush the power steering and hydro boost Click Here

Purchasing a 6.5 Diesel - Things to consider and How to purchase one.
  • 6.5L Buying Checklist: Here.
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Q
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R

Rear Axle Seal - How to repair leaking seals when there are gouges in the hub Here and Here

Rear End (G80) Lubricant Information GM TSB information on G80 rear end lubricant Here

Recall Information - There are many recalls out there, here are some info on them:

Resistor - PMD - See PMD Resistor

RPO codes - options that came with your vehicle. See glove box for sticker. These are three digit codes like: G80, L65, L56, etc.

Repair Manual - Military Repair Manual. This will download as an Adobe.pdf file Click Here

Runaway - Sudden acceleration without using the throttle pedal.
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S

Scan Tool: Tech2 is the GM Scan tool. It is very expensive to purchase though. There are other available software for the PC completely that emulates Tech2 functionality at a very reasonable price. For information about these programs see below:
  • '94-'95 OBD1 will need the GMTDScan Tech PC software and cable from ENGH Motors. How to make an interface cable
    Click Here or Click Here
  • GMTDScan Tech Issues:
    (a) Cant Install? Try installing In Windows Admin Mode Click Here
    (b) Cant Connect to PCM Click Here
  • '96-'00 OBD2 will need the Car Code, AutoEnginuity PC software and cable or AUTEL® MaxiDAS®, available on the net, all three service GM.
  • All 3 are very user-friendly, does everything the TECH2 does for engine and transmission test and control. All three connect to the USB port on a laptop computer.
  • Snap On MT2500 can be used for OBDII but there are some limitations: Click Here
How to set TDCO, go to: TDC Offset (Top Dead Center Offset)

Security System Relearn - Go to Theft Deterrent Learn

Serpentine Belt:

SES - see MIL

Sheared Cam Key - For more information about this Click Here.

Snorkel - Is the plastic intake inside of the passenger side fender, for more info Click Here.

Speedometer Calibration - Click Here for a mod to calibrate your speedometer if you are running a different gear ratio or larger sized tires.

Stalling - Common problem with the DS4 electronic injection pump system. Do a search for PMD's, lift pumps, OPS, etc. This problem may be electrical or in the fuel supply system. Thread to check out. To properly diagnose your stalling, use diagnostic checklist to pin point cause, no need to replace expensive parts that may not fix the problem.

Stanadyne Specs for IPs - Listing of Stanadyne Specs found Click here.

Starter
  • Intermittent No Crank - How To Diagnose Click Here
  • How To Repair Starter to Block Bolt Holes Click Here

Starter Bracket - Mounts on the front of the starter and the block. Essential for supporting the starter.
  • Part #9 In This Diagram Click Here
  • Parts List Click Here P/N for the gear reduction bracket is 23502557, P/N for the direct drive bracket is 14028931

Steaksauce - see A1, search "Steaksauce" to find info on this scammer.

Steering Stabalizer - Installation steps Here.

Stumbling - momentary loss of power, Check out See this thread Sometimes called fishbiting.
 

Attachments

#7 · (Edited)
FAQ T - Z

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T

T-Fitting/T-Valve - See "Water In Fuel Drain"

Tachometer - Device that indicates engine RPM. The signal for this gauge is derived from the alternator. Erratic reading from the tachometer may indicate a possible alternator problem. Follow proper diagnostics before determining if the alternator is at fault. The alternator pulley diameter is specific to the 6.5, so the wrong alternator pulley size will effect reading of tachometer as well.

TCC (Torque Convertor Clutch) - PCM modulates lockup according to requirements, Brake switch releases control. The TCC locks up under several conditions: brake switch off, engine temperature and speed. If your engine fails to meet these criteria, the TCC will not lock up.
  • If you would like to know how to manually lock the TCC on an OBDI truck Click here.
  • Why not to do the TCC lock up mod by GenBiltstein our 4l80E transmission guru Click Here
TDC Offset (Top Dead Center Offset) This is a factor the computer uses to compute timing for fuel injection.
Theft Deterrent Learn - Click here for procedure for an OBD-II.

Thermostat
  • Recommended Brands: AC Delco or Robert Shaw. Part numbers found in the 6.5L Parts List. All other aftermarket brands openings are too small for adequate coolant flow.
  • 180*F Thermostat - Pros & Cons Discussion Click Here
  • No Thermostat - What Are The Risks? Click Here

Throttle Position Sensor (Not APPS) - How to test and adjust the TPS on a pre 1994 truck Here

Torque Specs - Common Engine, Transmission & Differential Torque Specifications Click Here.

Towing - Many people tow with the 6.5. It may have its limits, but it makes for a decent truck.

Transfer Case

Transmission - Automatic - To get help with your automatic transmission:
Transmission - NV4500
Transmission - Other GM Manual Transmissions
Turbo - turbocharger) - The device that makes boost (more air pressure to the intake of the engine) from exhaust gas energy. See this thread.
(See also Wastegate for more information. Both are related)

  • To increase boost for the vacuum wastegate system see "Boost Fooler".
  • Information about the GM-X Turbo size can be Found Here.
  • Rebuilding the GM-X Turbo Found Here
  • Rebuilding the GM-8 Turbo Here

Turbo Heat Shield - Info and pictures Here

TurboMaster - a spring-operated wastegate controller that uses spring compression rather than vacuum to control turbo boost output. You can buy one at Heath Diesel, Kennedy Diesel, or make your own. They are all the same in principle, but different year trucks look different, so here's a few examples:

  • 1992-1993: GM3 turbo. Example here
  • 1992-1995: front-facing. Example here
  • 1996-2000: vertical. Examples here or here
TurboMaster Spring Rate- For the weight of spring to use on a Turbomaster Click Here.

_

U
_

V

Vacuum in Fuel Tank - Excessive vacuum in fuel tank is not a good situation. see Fuel cap, or read this thread.

Vacuum System & Pump - Belt driven device that creates vacuum source to run mostly the turbo wastegate system. If your vehicle is equipped with an EGR system, then the vacuum pump also provides a vacuum source for the operation of the valves and solenoids in the EGR system.
VSSB (Vehicle Speed Sensor Buffer) - Provides several factored frequency signals to PCM, ABS, and speedometer - divided frequencies are determined by soldered jumpers, to match tire sizing, differential gearing.
  • For information to modify your VSSB for an accurate speedometer, Click Here.

VIN Decoder - Click here
_

W

Wait to Start - Glow plug period time. Got no wait to start light? Look under Engine Coolant Temperature Sensor, Glow plug relay, and this thread on Engine Grounds.

Water In Fuel Drain - The factory "T-valve" is no longer available. For replacement options Click Here

Wastegate - The "flapper" valve that opens to bypass exhaust gasses around the turbine, thus reducing Boost to specified and safe level for engine operation.
Wastegate Solenoid - the computer operated solenoid valve that regulates the amount of vacuum going to the wastegate actuator on the turbo. This should hold the wastegate shut at idle. Not-so-common troubleshooting ideas to insure proper operation can be found here.
Wastegate solenoid refresh: Click Here

Water Pump - See Engine Cooling

White Smoke
- Some white smoke on cold start is normal. It should clear in a few seconds. If the white smoke continues:

(a) If the white smoke smells "sweet" - burning coolant

(b) If the white smoke smells like diesel fuel, there are two possible causes: failing injectors or lift pump. See this TSB regarding the Lift Pump Click Here

Windshield Washer
  • How to troubleshoot windshield washer pump Here
Windshield Wiper Delay Fix - GM wipers have a documented cold-solder problem on their circuit boards, often causing the wipers to stop working.

WMI - Water Mist Injection an alternative to using an intercooler. For more information:

  • Water Mist Injection Install with Pictures: See Here
  • Water Mist Injection Install: See Here
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X
_

Y
_

Z
 
#8 · (Edited by Moderator)
GM 6.5 FAQ, OBD Codes, DIY, Parts List & Info Sticky "Look In Here First"

1994 C/K Truck Shop Manual And 1994 Driveability, Emissions & Electrical Diagnosis Manuals


These are .pdf files which will download to your computer by selecting "Click Here"

Truck Shop Manual

Index Click Here
Section 0 - General Information: General Information, Maintenance & Lubrication, Vibration Diagnosis: Click Here
Section 1 - Heating and Air Conditioning: Click Here
Section 2 - Frame & Sheet Metal: Click Here
Section 3 - Steering, Suspension, Tires and Wheels: Click Here
Section 4 - Drive Shaft and Axles: Click Here
Section 5 - Brakes: Click Here
Section 6 - Engine:


    • General Information, Driveability and Diagnosis: Click Here
    • 6.5L Engine and Engine Mechanical Systems: Click Here
Section 7 - Transmission:
Section 8 - Electrical: Click here
Section 9 - Accessories: Audio Systems, Cruise Control, Engine Coolant Heater and Luggage Rack: Click Here
Section 10 - Body: Doors, Seats, Wiindows, Interior Trim, End Gate, Cab & Body Maintenance: Click Here

Driveability, Emissions (Diesel) & Electrical Diagnosis Manual

Section 1 - General Information: Click Here
Section 2 - Driveability Symptoms: Click Here
Section 3 - Control Module System: Click Here
Section 4 - Fuel System: Click Here
Section 5 & 6 (Gasoline Engines - Not Included)
Section 7 - Glow Plug System: Click Here
Section 8A - Electrical Diagnosis:

Section 9 - Exhaust Gas Recirculation (EGR) System: Click Here
Section 10 - Transmission: Click Here
Section 11 - Crankcase Ventilation System: Click Here
Section 12 - Air Intake System: Click here




__
 

Attachments

#9 · (Edited)
GM 6.5 FAQ, OBD Codes, DIY, Parts List & Info Sticky "Look In Here First"

1996 C/K Truck Shop Manual and 1996 Driveability, Emissions & Electrical Diagnosis Manuals

These are .pdf files which will download to your computer by selecting "Click Here"

Truck Shop Manual

Index Click Here
Section 0 - General Information: General Information, Maintenance & Lubrication, Vibration Diagnosis: Click Here
Section 1 - Heating and Air Conditioning: Click Here
Section 2 - Frame & Sheet Metal: Click Here
Section 3 - Steering, Suspension, Tires and Wheels: Click Here
Section 4 - Drive Shaft and Axles: Click Here
Section 5 - Brakes: Click Here
Section 6 - Engine: Click Here

Section 7 - Transmission: Section 8 - Electrical: Click here
Section 9 - Accessories: Audio Systems, Cruise Control, Engine Coolant Heater and Luggage Rack: Click Here
Section 10 - Body: Doors, Seats, Wiindows, Interior Trim, End Gate, Cab & Body Maintenance: Click Here

Electrical Diagnosis Manual

Section 8A - Electrical Diagnosis:
 

Attachments

#10 · (Edited)
1995 C/K Truck Shop Manual, 1995 HVAC and Drive Shaft-Axle Supplement, and 1995 Driveability, Emissions & Electrical Diagnosis Manuals

These are .pdf files which will download to your computer by selecting "Click Here"

Truck Shop Manual

Index Click Here
Section 0 - General Information: General Information, Maintenance & Lubrication, Vibration Diagnosis: Click Here
Section 1 - Heating and Air Conditioning: Click Here
Section 2 - Frame & Sheet Metal: Click Here
Section 3 - Steering, Suspension, Tires and Wheels: Click Here
Section 4 - Drive Shaft and Axles: Click Here
Section 5 - Brakes: Click Here
Section 6 - Engine:
  • General Information, Driveability and Diagnosis: Click Here
  • 6.5L Engine and Engine Mechanical Systems: Engine Cooling, Radiator, Fuel Systems, Fuel Injection, Engine Electrical, Battery, Cranking System, Charging System & Ignition System Click Here
  • 6.5L Engine and Engine Mechanical Systems: Glow Plug Electrical System, Emissions, Exhaust System, Vacuum Pump & Turbocharger Click Here
Section 7 - Transmission: Section 8 - Electrical: Click here
Section 9 - Accessories: Audio Systems, Cruise Control, Engine Coolant Heater and Luggage Rack: Click Here
Section 10 - Body: Doors, Seats, Wiindows, Interior Trim, End Gate, Cab & Body Maintenance: Click Here

1995 HVAC and Drive Shaft-Axle Supplement Click here

Driveability, Emissions (Diesel) & Electrical Diagnosis Manual

Section 1 - General Information: Click Here
Section 2 - Driveability Symptoms: Click Here
Section 3 - Control Module System: Click Here
Section 4 - Fuel System: Click Here
Section 5 & 6 (Gasoline Engines - Not Included)
Section 7 - Glow Plug System: Click Here
Section 8A - Electrical Diagnosis:
Section 9 - Exhaust Gas Recirculation (EGR) System: Click Here
Section 10 - Transmission: Click Here
Section 11 - Crankcase Ventilation System: Click Here
Section 12 - Air Intake System: Click here




__________

1995
 

Attachments

#11 · (Edited)
GM 6.5 FAQ, OBD Codes, DIY, Parts List & Info Sticky "Look In Here First"

1997 C/K Truck Shop Manual and 1997 Electrical Diagnosis Manual

These are .pdf files which will download to your computer by selecting "Click Here"

Truck Shop Manual

Index Click Here
Section 0 - General Information: General Information, Maintenance & Lubrication, Vibration Diagnosis: Click Here
Section 1 - Heating and Air Conditioning: Click Here
Section 2 - Frame & Sheet Metal: Click Here
Section 3 - Steering, Suspension, Tires and Wheels: Click Here
Section 4 - Drive Shaft and Axles: Click Here
Section 5 - Brakes: Click Here
Section 6 - Engine:
Section 7 - Transmission: Section 8 - Electrical: Click here
Section 9 - Accessories: Audio Systems, Cruise Control, Engine Coolant Heater and Luggage Rack: Click Here
Section 10 - Body: Doors, Seats, Windows, Interior Trim, End Gate, Cab & Body Maintenance: Click Here

Electrical Diagnosis Manual

Section 8A - Electrical Diagnosis: Click Here






.
 

Attachments

#14 · (Edited)
GM 6.5 FAQ, OBD Codes, DIY, Parts List & Info Sticky "Look In Here First"

1999 C/K Truck Shop Manual

These are .pdf files which will download to your computer by selecting "Click Here"

Index Click Here
Section 0 - General Information: General Information, Maintenance & Lubrication, Vibration Diagnosis: Click Here
Section 1 - Heating and Air Conditioning: Click Here
Section 2 - Steering: Click Here
Section 3 - Suspension, Tires and Wheels: Click Here
Section 4 - Driveline and Axles: Click Here
Section 5 - Brakes: Click Here
Section 6 - Engine:

Section 7 - Transmission: Section 8 - Body and Accessories
  • Contents: Click Here
  • Pages: 1 - 599: Click Here for: Lighting Systems, Wipers/Washer, Entertainment, Wiring, Cellular Communication and Body Control System
  • Pages: 600 - 953: Click Here for: Body Control System (continued), Instrument Panel/Gauges and Console, Keyless Entry, Horn, Theft Deterrent, Cruise Control, Garage Door Opener, Exterior Trim, Water Leaks, Air/Wind Noise, Squeaks & Rattles and Stationary Windows
  • Pages: 954 - 1,303: Click Here for: Bumpers, Body Front End, Doors, Roof, Seats and Interior Trim
  • Pages: 1,304 - 1,460: Click Here for: Interior Trim (continued), Body Rear End, Plastic Panel Information & Repair, Paint/Coatings and Frame & Underbody
Section 9 - Restraints: Click Here







.
 

Attachments

#13 · (Edited)
GM 6.5 FAQ, OBD Codes, DIY, Parts List & Info Sticky "Look In Here First"

1998 C/K Truck Shop Manual

These are .pdf files which will download to your computer by selecting "Click Here"

Index Click Here
Section 0 - General Information: General Information, Maintenance & Lubrication, Vibration Diagnosis: Click Here
Section 1 - Heating and Air Conditioning: Click Here
Section 2 - Steering: Click Here
Section 3 - Suspension, Tires and Wheels: Click Here
Section 4 - Driveline and Axles: Click Here
Section 5 - Brakes: Click Here
Section 6 - Engine:

Section 7 - Transmission: Section 8 - Body and Accessories
  • Contents: Click Here
  • Pages: 1 - 244: Click Here for: Lighting, Wipers/Washer,Entertainment Systems and Keyless Entry
  • Pages: 245 - 608: Click Here for: Wiring, Instrument Panel/Gauges and Console
  • Pages: 609 - 836: Click Here for: Horn, Theft Deterrent, Cruise Control, Garage Door Opener, Exterior Trim, Water Leaks, Air/Wind Noise, Squeaks & Rattles, Stationary Windows and Bumpers
  • Pages: 837 - 1,132: Click Here for: Doors, Roof, Seats and Interior Trim
  • Pages: 1,133 - 1,258: Click Here for: Body Rear End, Plastic Panel Information & Repair, Paiint/Coatings and Frame & Underbody
Section 9 - Restraints: Click Here







.
 

Attachments

#15 · (Edited)
OBDI and OBDII Information

OBDI and OBDII Information:

OBD1 Codes
  • List of OBDI Codes Here

    [*]1994 DTC Diagnostics and Procedures Manual (.pdf file) Here

    [*]1995 DTC Diagnostics and Procedures Manual (.pdf file) Here

OBDII Codes

  • List of OBDII Codes Here

  • 1996 DTC Diagnostics and Procedures Manual (.pdf file) Here

  • 1997 DTC Diagnostics and Procedures Manual (.pdf file) Here

  • 1998 DTC Diagnostics and Procedures Manual (.pdf file) Here

  • 1999 DTC Diagnostics and Procedures Manual (.pdf file) Here

DTC Look Up Tool Here
 
#17 · (Edited)
1992 & 1993 C/K Trucks

Part #1 Parts catalog
Part #2 Illustration catalog

The files are too large for our servers to upload here but the site links to the downloadable PDF files can be found here: Click Here




1991 Student Handbook This is a condensed version of the GM Factory Service Manual. Covers 1992-1993 6.5L TD trucks with the DB2 injection pump. This is a .pdf file: Click Here

Technical Service Bulletins:
These are .pdf files:

Fuel Systems, Driveability, Air/Fuel Filters:

TSB 93-286-6A - Stalling/Hesitation/Low Power/White Smoke (Check Lift Pump/Condition: New Oil Pressure Sender/Switch Available): Click Here

TSB 376303 - Use of Low Sulfur Diesel Fuel: Click Here

TSB 57-63-03 - Possible Internal Cylinder Damage Due To Glow Plug Breaking After Replacing Fuel Injector Nozzle: Click Here

Brakes:

TSB 00-05-22-004 - Brake fluid Level and Filling Recommendations: Click Here

TSB 46-50-06 - Early Brake Pad Wear and/or Tire Wear (New Steering and Brake Systemm Components: Click Here

TSB 56-50-04 - Parking Brake C3500HD Trucks: Click Here

TSB 86-50-20A- Brake Lead/Pull and Front Brake Wear (Replace Rear Brake Shoes) REVISED: Click Here

TSB 99-05-001A- Brake Lead/Pull and Front Brake Wear (Replace Front Brake Pads and Rear Brake Shoes) REVISED: Click Here

TSB 345001- Four Wheel Antilock Brake System: Click Here

TSB AE93IBA08- Replacement of Suspect GMSCMs In ABS Units: Click Here















.
 

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