Diagnostic Aids

WARNING: This page is about a different car, the 2008 GMC Sierra and 2008 Chevrolet Silverado. 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.