Inoperative 4WD AWD Lamp - Update to TSB 02-04-21-006

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

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.

Inspect and verify no communication with the TCCM.

If no communication:

1. 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.
2. Wait 30 seconds and reinstall the fuse.
3. 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.
4. 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.