| Subject: | Electronic Transfer Case Unable to Complete Shift |
| Models: | 1999-2000 Cadillac Escalade |
| 2002-2007 Chevrolet Avalanche, Trailblazer |
| 2004-2007 Chevrolet Colorado |
| 1999-2005 Chevrolet Blazer, S10 |
| 1999-2007 Chevrolet Silverado, Suburban, Tahoe |
| 1999-2007 GMC Envoy, Sierra, Yukon, Yukon Denali, Yukon XL, |
| 1999-2005 GMC Jimmy, Sonoma |
| with RPOs NR4, NP1, or NP8 Transfer Case |
PI is being created to update models and years. Please discard PIP3424
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Electronic transfer case may stop shifting if you repeatedly try to shift the transfer case in a short period of time and not set any dtcs
Recommendation/Instructions:
The software in the transfer case control module has a "shift abuse lock out" mode to protect the module and encoder motor. This concern will occur if the module senses repeated shift request in a short period of time. If the driver continuously tries
to shift in and out of different modes, the transfer case control module will stop trying to shift for several seconds to prevent abuse damage to occur. Cycling the ignition off for 30 seconds or more should allow the transfer case to resume normal operation.
Please follow this diagnostic or repair 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.
