Conditions for Setting the DTC
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The heater line voltage is more than 8.1 volts with the relay OFF.
OR
The heater line voltage is between 3.8-8.1 volts with the ignition OFF.
AND
The heater line voltage is less than 0.5 volt below battery voltage with the ignition ON.
OR
The heater line voltage is less than 3.8 volts with the relay OFF.
AND
The reference line voltage is low with the relay OFF.