Theory of Operation

By running the Actuator Circuit Test / Door Calibration Function, the A/C Heater Control can identify up to three door driver circuits shorted simultaneously. A DTC 72 will set if more than three door driver circuits are shorted in the same direction (e.g. four door driver circuits all shorted to ground) or if two or more door driver circuits are shorted with at least one door driver circuit shorted to ignition and one door driver circuit shorted to ground. To ensure a proper diagnosis, diagnose and repair Actuator Circuit Test faults in the following order: If present, diagnose and repair DTC 72 first, then DTC 62, then DTC 61, then DTCs 64, 68, or 71, and finally DTCs 63, 67, or 69. In addition, always test the door driver circuits after each repair by clearing DTCs, and then running the Actuator Circuit Test / Door Calibration Function, and then checking for DTCs.

• When Monitored: 

  When running the Actuator Circuit Test / Door Calibration Function.

• Set Condition: 

  If the A/C Heater Control detects a short to ground on the (C255) Left Blend Door Driver circuit.