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Makes 🢒 GMC_Truck 🢒 2003 🢒 GMC K Sierra - 4WD (CNG) 🢒 Bulletins 🢒 Adm Msg - Inoperative 4WD/AWD or Service 4WD Indicator (Admin Number VSS20020131 10/4/02)

Adm Msg - Inoperative 4WD/AWD or Service 4WD Indicator (Admin Number VSS20020131 10/4/02)

Subject:Adm Msg -- Inoperative 4WD/AWD or Service 4WD Indicator (Admin Number VSS20020131 -- 10/04/02)

Models:Chevrolet Silverado, Tahoe, Suburban, Avalanche, TrailBlazer, TrailBlazer EXT; GMC Sierra, Yukon, Yukon XL, Envoy, Envoy XL; Oldsmobile Bravada
With RPO Codes: NP8 - Autotrack Transfer Case; NP4 - Autotrack Transfer Case; NP1 - Electric Shift Transfer Case


Important: Corporate Bulletin Number 02-04-21-006A will supersede this message.

Customer Concern

Some customers may comment that the service 4WD indicator is on, or the 4WD system is inoperative.

Cause

The 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.

Correction

Remove the underhood TCCM fuse (labeled ATCM or TREC). Wait 30 seconds and then reinstall the fuse. The module should "wake up" and communicate with the Tech 2. Reprogram the TCCM using normal SPS procedures, using operating system calibration number 12580062 (or the most current calibration).