Technical Service Bulletins

Sleepy 4WD

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Sleepy 4WD

Owners of 2002 Chevy Silverado K 4WD vehicles may complain that the 4WD system is inoperative and that the service 4WD indicator is on.

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.

Remove the underhood TCCM fuse (labeled ATCM or TREC). Wait for 30 seconds and 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).

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