Thanks for the information link. I have been through the process of shifting into 4 low with the transmission in neutral and the truck moving at less than 3 mph. It just doesn't want to shift to 4 low. Light blinks and then eventually goes out and the light returns to what ever position it was on prior to the attempted shift.
Document ID# 1656808
2005 GMC Truck GMC K Sierra - 4wd
Subject: Electronic Transfer Case Unable to Complete Shift
keywords 226 236 246 263 246EAU 263 EAU 4482 4484 blink flash inoperative light module NP1 NP8 NR4 switch TCCM #PIP3424 - (05/11/2005)
Models:
1999-2000
Cadillac Escalade
2002-2005
Chevrolet Avalanche, Trailblazer
2004-2005
Chevrolet Colorado
1999-2004
Chevrolet Blazer
1999-2005
Chevrolet Silverado, Suburban, Tahoe
2004-2005 GMC Canyon
1999-2005 GMC Envoy, Sierra, Yukon, Yukon Denali, Yukon XL
1999-2004 GMC Jimmy
1999 GMC Suburban
2003-2005 Hummer H2
with RPOs NR4, NP1, or NP8 Transfer case
The following diagnosis might be helpful if the vehicle exhibits the symptoms(s) described in the PI.
Condition/concern:
Electronic transfer case may stop shifting if you repeatedly try to shift the transfer case in a short period of time.
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 requests 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 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.
Keep us posted on your Sierra and hope this helps
Molson02536
