GM Service Manual Online
For 1990-2009 cars only

NVG246 NP8 4WD Inoperative DTC C0308 ATC Fuse Open - keywords case cold electrical ground hi4 hot lamp light lo4 no switch TCM transfer U1016 U1026 U1041 U1064 U1301 wire

Subject:NVG246 NP8 4WD Inoperative DTC C0308 ATC Fuse Open

Models:1999-2000 Cadillac Escalade
1998-1999 Chevrolet Pickup
1999-2002 Chevrolet Silverado
1998-2002 Chevrolet Suburban, Tahoe
2000 GMC Denali
1998-1999 GMC Pickup, Suburban
1998-2001 GMC Sierra
1998-2002 GMC Yukon
2000-2002 GMC Yukon XL



The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.

Condition/Concern:

Four wheel drive inoperative and the 4WD service light will illuminate. Diagnosis may reveal that the ATC fuse could be open, possible DTC C0308, or various "U" codes may be set. The encoder motor may also be shorted or the TCCM may be damaged.

Recommendation/Instructions:

Perform a component check to ensure the encoder motor is not damaged. Verify TCCM and encoder motor ground integrity. Refer to the applicable schematics for the TCCM and encoder motor grounds. If the TCCM and Encoder motor ground integrity are good, check grounds G102 and G107. Refer to the shop manual or eSI for the location of G102 and G107.

The transfer case schematics will not show grounds G102 and G107. These grounds are various engine, chassis and body grounds. If G102 and G107 are loose the TCCM and possibly the encoder motor are being used as a ground path.

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.