Z71 4wd warning light

ozbeau · November 14, 2006

My 2003 z71 is showing warning light "service 4wd" and the automatic transfer case buttons will not light up. It is in 2wd and drives ok. What is going on here? Maybe a fuse? thanks oz

GM-Tech · November 14, 2006

If doing as described in the following doesn't help, further diagnosis will be needed. That would include test equipment that you likely do not have available to you. Try this...

Subject: Inoperative 4WD AWD Lamp - Update to TSB 02-04-21-006 #PI00462A - (09/30/2002)

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Condition/Concern:

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 indicator is on.

Recommendation/Instructions:

Inspect and verify no communication with the TCCM.

If no communication:

Pull the TREC fuse or the ATC fuse under the hood. Depending on application you will have one or the other fuse located in the underhood electrical center.

Wait 30 seconds and reinstall the fuse.

If you can communicate with the Tech 2, use the calibration below. If you cannot communicate with the Tech 2 check for other issues and replace the TCCM.

Reprogram the TCCM with calibration # 12580062.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information 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 condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

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