Conditions for Setting the DTC

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The system monitors the voltage on the 4 high indicator control circuit.
The TCCM detects 1.6 V or less for 1.5 seconds when the 4 High indicator is commanded ON.
The TCCM detects 3.4 V or more when the 4 High indicator is commanded OFF.