Conditions for Setting the DTC
WARNING: This page is about a different car, the 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
The transfer case shift control module has a predefined range in which the encoder feedback should stay within, which is 0.5-4.5 volts. The DTC sets if the encoder signal feedback falls out of this range.