Conditions For Setting DTC
WARNING: This page is about a different car, the 2002 Pontiac Grand Prix, 2002 Chevrolet Malibu, and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
The PCM detects that the heater control circuit current is greater than the capacity of the PCM internal driver for more than 20 seconds.