Conditions for Running the DTC

WARNING: This page is about a different car, the 2007 GMC Sierra, 2007 GMC Cab & Chassis Sierra, 2007 Chevrolet Silverado, and 2007 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The IAH is commanded ON.
The IAH battery voltage is more than 6.9 volts.
GPCM ignition voltage is more than 6.9 volts.
DTC 154C runs continuously when the above conditions are met.