Conditions for Setting the DTC
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The TBCM detects voltage greater than 5.2 volts in the manual apply switch 5 volt reference circuit.
The TBCM detects voltage less than 4.8 volts in the manual apply switch 5 volt reference circuit.