Question about 1998 GMC Sierra

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Where is the transfer case control module on 98 gmc sierra

I think I need to replace the transfer case control module but having difficulty in locating it.

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  • Kyle Lauf Nov 25, 2012

    It is not there. Can you be more specific? If sitting in the passengers seat the area by your feet under the glove box is the heater and the blower motor. At right side where your feet sit next to the door there is a grey cover that I opend up and there is nothing there.

  • Kyle Lauf Nov 29, 2012

    I found the module it is located on Driver side to the left of the steering wheel will post pictures later.

  • Anonymous Mar 26, 2014

    controls the signal to the transfer case


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It is located under the passenger side kick panel. Remove the plastic kick panel cover to reveal the TCCM.

Posted on Nov 02, 2012

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Posted on Jan 02, 2017

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SOURCE: Ned to change the oil in transfer case

The Z71 typically comes with the auto 4wd transfer case (cannot remember the GM number). This requires AutoTrak II, which is available at a GM dealer. Do not use any other fluid in this transfer case! The previous post was correct in the location of the two plugs, but not on the fluid (the other types of transfer cases by GM use ATF). The transfer case is located under the truck right under the cab. There is a small skid plate under it, and a large driveshaft leaves the rear end of the case heading to the rear differential (axle). If you have the manual or electronic w/o auto 4WD transfer case, you can use Dexron III, but Dexron VI is a better fluid that is also now available at your local auto parts store. Again, if you have the AUTO 4WD button in the dash, use the AutoTrak II fluid from the dealer.

Posted on May 22, 2009

  • 1 Answer

SOURCE: transfer case control module

Its behind the kick panal on the pssengers side.

Posted on Nov 25, 2008

  • 3 Answers

SOURCE: I have an 1991 gmc sierra K1500 4x4 my transfer

Try Replacing the Transfer Case.

Posted on Nov 20, 2009

  • 523 Answers

SOURCE: replace neutral safety switch on a 1988 gmc sierra

Typically the Neutral Safety Switches are located with the gear selector, either in the column or the floor.

Hope this helps,

Posted on Aug 21, 2009

  • 1 Answer


I have the same issue...what's the fix?

Posted on Oct 01, 2008

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1 Answer

2007 gmc 1500 4wd not working. service light on and lights on switches are off. truck in 4 low

Sounds as if the transfer case control module has gone bad and grounded the circuit to the 4 low actuator. The module is located behind the headlight switch in the dash. You could try tapping the actuator on the transfer case lightly with a hammer to see if it releases.

Feb 23, 2015 | 2007 GMC Sierra 1500

1 Answer

2005 gmc sierra 4wd warning light on and will not shift into 4wd

been here /transfer case control module/ electric -shift /actually easy fix /under left sideof instrument panel.behind headlight switch.if thats not it/electric shift motor and encoder assembly /sounds confusing but its easy fix to .get u a repair manual youll see.good luck.

Jan 08, 2013 | 2005 GMC Sierra

1 Answer

Service 4wd light appears on message box and the push buttons won't work. how can i find the problem in a cheap way? I don't really have money to blow on replacement parts. It's a 99'...

THis information from TS Bulletin...

Subject: "Service 4WD" Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch)
Models: 1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL)
with Four Wheel Drive and NVG 236/246 Transfer Case (RPO NP8)

Condition: Some customers may comment on the Service 4WD indicator illuminating. Upon investigation, the technician may find DTC B2725 set.

Cause: The condition may be due to a intermittent fault in the transfer case shift control switch.

Important: The transfer case shift control module should not need replacement. DO NOT replace P/N 15749703 unless diagnosis points to the module as the malfunction.

Replace the transfer case shift control switch using published Service Information procedures.

Hope this helps; also keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer. Thank you for using Fixya, and have a nice day.

Oct 19, 2011 | 1999 Chevrolet Silverado 1500

1 Answer

2002 envoy code co550

you need to replace the tccm and get it programmed.

2-04-21-006E: Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System, DTC C0550 Set No Communication with TCCM (Reprogram Transfer Case Control Module) - (Jul 20, 2006)
999999995.gif Subject: Inoperative 4WD/AWD Lamps, Inoperative 4WD/AWD System, DTC C0550 Set, No Communication with TCCM (Reprogram Transfer Case Control Module) Models: 2004 Buick Rainier 2002-2004 Chevrolet TrailBlazer, TrailBlazer EXT 2003-2004 Chevrolet Avalanche, Silverado, Suburban, Tahoe 2002-2004 GMC Envoy, Envoy XL 2003-2004 GMC Sierra, Yukon, Yukon XL 2004 GMC Envoy XUV 2002-2004 Oldsmobile Bravada with Electronic Shift or Active Transfer Case (RPOs NP1, NP4 or NP8)

This bulletin is being revised to add Subject information and change the labor operation. This bulletin cancels and supersedes Bulletin Number 03-04-21-006. Please discard Corporate Bulletin Numbers 02-04-21-006D and 03-04-21-006 (Section 04 -- Driveline/Axle).
ConditionSome customers may comment that the 4WD/AWD indicator lights on the selector switch do not work, or the 4WD/AWD system may be inoperative and/or the service 4WD light is illuminated. The condition is typically intermittent and always occurs at key-up. Upon investigation, the technician may find DTC C0550 set.
CauseThe Transfer Case Control Module (TCCM) has not received the wake-up call during key-up and has remained in the "sleep mode".
When the TCCM is in the "sleep mode", it will not communicate with the class II bus or the Tech 2®.
  1. Try to communicate with the TCCM. If no communication, go to step 2. If communication is possible, go to step 5.
  2. Remove the underhood (ATCM or TREC) TCCM fuse.
  3. Wait 30 seconds.
  4. Reinstall the fuse. The module should "wake up" and communicate with the Tech 2®.
  5. Check for codes in the TCCM. If a C0550 is found current or in history with or without other codes, replace the module and go to step 6.
  6. Reprogram the TCCM with the latest TIS software using normal SPS procedures.
  7. Verify operation and that no codes are present.
Important: For the 2002 model year, the TCCM must be replaced and reprogrammed.
Warranty Information

Jul 29, 2011 | 2002 GMC Envoy

1 Answer

I have a 1998 gmc sierra 4x4 extended cab. i just replaced the rear end in it. on the way home i lost drive and o/d and now the push button transfer case doesn't want to work.

Hi, the transfer case has an encoder motor , that shifts it. When a problem occurs, it can go haywire, and make it so it will not shift. Sometimes if you disconnect the battery for a minute,and reattach, the transfer case control module can reset, and allow function. the typical issues are the switch, the module, and the encoder motor. This could be a costly situation, if you replace parts hoping for the best, iit should be diagnosed at a shop with a scanner, I think in the long run, this may save you money, knowing where to go. Try the battery thing first, because sometimes it can be a fluke, and this can fix it. Thanks..coop442000

Sep 25, 2010 | 1998 GMC Sierra

1 Answer

Just replaced my encoder motor, front actuator, and dash switch....altough the transfer case engages it won't stay in 4 wheel drive for long

you may have to replace your trasfer case control module its right under dash driver side easy to access mine just went out it was throwing c0359 code 4 low cirut and service four wheel drive would come on dash although the 4wd works great it just throws the code.

Jan 01, 2010 | 2003 GMC Sierra

1 Answer


when you replaced the module did you notice any corrosion in the connector green powder
also check the connector at the encoder motor
high resistance in the wiring will cause it not to get the right information
if the wiring is good try a switch
hope this helps you
good luck let me know

Nov 12, 2009 | 1997 GMC Sierra

1 Answer

I have a 2005 GMC Sierra. After driving for a couple of miles the 'service 4wd' warning will display and not go away. The 4wd is fine. Do I need to reset a chip?


Jul 20, 2009 | 2005 GMC Sierra

1 Answer

2002 gmc 2500 4wd truck

This DTC detects a short to voltage in the Motor Control A or Motor Control B circuits, or a shorted motor.
The transfer case motor is a bi-directional, permanent magnet, D.C. motor. When energized, (through Motor Control A or Motor Control B, the ground is provided by the opposing Motor Control circuit and then grounded through the transfer case shift control module ground circuit), the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between 4H, AUTO 4WD, 2H, N, and 4L ranges. While the transfer case motor is energized the transfer case shift control module also energizes the solenoid for the transfer case lock. The motor lock is disabled (locking action released) and free turning of the transfer case motor and sector shaft is then allowed.

Conditions for Setting the DTC
• The system will test the motor circuits by reading the voltage on each circuit.
• If the system detects a problem with the circuits, the DTC is logged.
• The transfer case shift control module senses a high voltage in the Motor Control A or Motor Control B circuits when a low voltage is expected.
Action Taken When the DTC Sets
• All shifting will be disabled.
• The SERVICE 4WD indicator will be latched on for the remainder of the current ignition cycle.
Conditions for Clearing the DTC
• The transfer case shift control module will clear the DTC if the condition for setting the DTC no longer exists.
• A history DTC will clear after 100 consecutive ignition cycles without a fault present.
• History DTCs can be cleared using a scan tool.

Schematic Reference: Transfer Case Control Schematics
Was the Transfer Case Diagnostic System Check performed?
Go to Step 2
Go to Diagnostic System Check - Transfer Case
Check the transfer Case shift control module for faulty power or grounds. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
Go to Step 9
Go to Step 3
Install a scan tool.
Turn ON the ignition, with the engine OFF.
With the scan tool, command the Motor A/B control ON and OFF.
Does the encoder motor turn ON and OFF?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 4
Turn the ignition OFF.
Disconnect the four wire connector at the transfer case.
Turn the ignition ON, with the engine OFF.
Connect a DMM between the Motor Control A circuit harness connector and ground at the transfer case.
Is the voltage reading within the specified value?
0-0.2 V
Go to Step 5
Go to Step 6
Connect a DMM between the Motor Control B circuit harness connector and ground at the transfer case.
Is the voltage reading within the specified value?
0-0.2 V
Go to Step 8
Go to Step 7
Disconnect the transfer case shift control module.
Test the Motor Control A circuit harness connector for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
Go to Step 9
Go to Step 8
Disconnect the transfer case shift control module.
Test the Motor Control B circuit harness connector for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Was the condition found and corrected?
Go to Step 9
Go to Step 8
Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
Is the repair complete?
Go to Step 9
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
Go to Step 2
System OK

Jun 16, 2017 | 2002 GMC Sierra

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