Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

The incremental position sensor and the rotational position sensor both show position in degrees. Monitor these parameters for erratic or unreasonable readings.
A Key ON, engine OFF sequence with transfer case encoder motor removed, but still attached to the harness, will cause C0398 5A to set.
Repeatedly commanding the TCEM forward or reverse without pressing the exit button between commands, to return to the "none" state, can result in incorrect readings.