Conditions for Setting the DTC

WARNING: This page is about a different car, the 2007 Hummer H2. However, it is still accessible from the selected car via links, so may be relevant.

After the transfer case shift control module grounds the output, the 4WD low circuit, and reads back a high voltage, the DTC is set. The system will not attempt setting the DTC again during that ignition cycle.
The transfer case shift control module reads back a high voltage when a low voltage is expected on the 4WD low circuit.