Conditions for Setting the DTC

WARNING: This page is about a different car, the 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

The transfer case shift control module will try to unapply, turn off the lock solenoid by grounding the motor control circuit.
If the module does not see battery voltage at the motor lock control circuit prior to applying the motor lock the DTC will set.
Transfer Case Lock output reads back as a high voltage when a low voltage is expected.