03 Silverado 1500 w NP8 transfer case and 5.3 L motor. DTC code C0306 is set.
2WD/4WD shifting is disabled and 2WD light on switch panel is lit. Using procedures in GM manual, encoder motor seems ok, but found 'short to voltage' condition on motor A control circuit. Also, motor A and motor B control channels measure 108 ohm and 42k ohm to ground. But, wiring harness seems not to have any physical faults (shorts, etc.)
Much written about this transfer case in several GM vehicles and model years, but nothing helpful. Info from NTSB/NHTSA suggests examining some engine and chassis grounds. Hard to do, but all seems ok although I have not checked ALL grounds yet.
Can the transfer case control module (>$300 for a new one from GM plus programming) fail in such a way as to produce the test results above? other possibilities?