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Discussion Starter #1
Helping my bro-in-law with his 2012 Sierra 1500. The transfer case appears to be stuck in neutral. The check 4wd message is on and we're getting C0306, C0321, and C0396 code, all indicating an issue with the shift motor. I bench-tested his motor and it did not do anything that AllData says it should, so we figured that was his problem. We replaced it with no improvement. I also tested all the circuits in the harness. Initially I found power on one circuit coming from the TCCM that should have been ground, indicating a short. The short went away when I disconnected the TCCM and reappeared when I reconnected it. So we replaced the TCCM as well and that short did go away. But the overall symptoms have not changed. Occasionally you can start the truck up and it will catch a gear briefly but the gear "fades" to neutral before you can even get out of the driveway.

I'm aware that there are 2 reprogramming procedures, one for clutch high / low learning which can e done without a scanner. We can not get the truck to perform that procedure. (Key in accessory position, hold t-case shift knob in neutral for 30 seconds.) The other can only be done by a dealer.

Anyone encountered this before? Only thing left to replace is the switch but all codes point to the motor.
 

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Premium Member
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Discussion Starter #2
Finally got the high / low learning procedure to work and our 3 main codes are gone only to be replaced by a C0387 now. Again, pointing toward short in motor.
 
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