2007 Commander XK Factory Service Manual 24 - HEATING & AIR CONDITIONING

72-SHORT TOO COMPLEX (MTC)





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


NOTE: This DTC will display as active if the ignition is not cycled after running the Actuator Circuit Test / Door Calibration Function. Otherwise, it will display as stored until cleared.

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, 66, 68, or 71, and finally DTCs 63, 65, 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.

Possible Causes
 
MORE THAN THREE DOOR DRIVER CIRCUITS SHORTED TO VOLTAGE
 
MORE THAN THREE DOOR DRIVER CIRCUITS SHORTED TO GROUND
 
TWO OR MORE DOOR DRIVER CIRCUITS SHORTED WITH AT LEAST ONE SHORTED TO IGNITION AND ONE SHORTED TO GROUND
 
FRONT MODE DOOR ACTUATOR
 
SECOND ROW MODE DOOR ACTUATOR
 
LEFT BLEND DOOR ACTUATOR
 
RECIRCULATION DOOR ACTUATOR
 
A/C HEATER CONTROL
 




Diagnostic Test

1. CHECK THE (C266) FRONT MODE DOOR DRIVER CIRCUIT, (C66) FRONT MODE DOOR COMMON DRIVER CIRCUIT, (C139) SECOND ROW MODE DOOR DRIVER CIRCUIT, (C939) SECOND ROW MODE DOOR COMMON DRIVER CIRCUIT, (C255) LEFT BLEND DOOR DRIVER CIRCUIT, (C55) LEFT BLEND DOOR COMMON DRIVER CIRCUIT, (C268) RECIRCULATION DOOR DRIVER CIRCUIT, & (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO VOLTAGE



Turn the ignition off.
Disconnect the A/C Heater Control C2 harness connector.
Turn the ignition on.
Measure the voltage of the (C266) Front Mode Door Driver circuit, (C66) Front Mode Door Common Driver circuit, (C139) Second Row Mode Door Driver circuit, (C939) Second Row Mode Door Common Driver circuit, (C255) Left Blend Door Driver circuit, (C55) Left Blend Door Common Driver circuit, (C268) Recirculation Door Driver circuit, and the (C68) Recirculation Door Common Driver circuit.

Is the voltage above 0.2 volts on any of the circuits?

Yes


No

2. CHECK THE (C266) FRONT MODE DOOR DRIVER CIRCUIT, (C66) FRONT MODE DOOR COMMON DRIVER CIRCUIT, (C139) SECOND ROW MODE DOOR DRIVER CIRCUIT, (C939) SECOND ROW MODE DOOR COMMON DRIVER CIRCUIT, (C255) LEFT BLEND DOOR DRIVER CIRCUIT, (C55) LEFT BLEND DOOR COMMON DRIVER CIRCUIT, (C268) RECIRCULATION DOOR DRIVER CIRCUIT, & (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO GROUND



Turn the ignition off.
Measure the resistance of the (C266) Front Mode Door Driver circuit, (C66) Front Mode Door Common Driver circuit, (C139) Second Row Mode Door Driver circuit, (C939) Second Row Mode Door Common Driver circuit, (C255) Left Blend Door Driver circuit, (C55) Left Blend Door Common Driver circuit, (C268) Recirculation Door Driver circuit, and the (C68) Recirculation Door Common Driver circuit between ground and the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms on any of the circuits?

Yes


No

3. CHECK THE (C266) FRONT MODE DOOR DRIVER CIRCUIT FOR A SHORT TO THE (C139) SECOND ROW MODE DOOR DRIVER CIRCUIT, (C939) SECOND ROW MODE DOOR COMMON DRIVER CIRCUIT, (C255) LEFT BLEND DOOR DRIVER CIRCUIT, (C55) LEFT BLEND DOOR COMMON DRIVER CIRCUIT, (C268) RECIRCULATION DOOR DRIVER CIRCUIT, & THE (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT



Measure the resistance between the (C266) Front Mode Door Driver circuit and the (C139) Second Row Mode Door Driver circuit, (C939) Second Row Mode Door Common Driver circuit, (C255) Left Blend Door Driver circuit, (C55) Left Blend Door Common Driver circuit, (C268) Recirculation Door Driver circuit, and the (C68) Recirculation Door Common Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms on any of the circuits?

Yes


No

4. CHECK THE (C66) FRONT MODE DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO THE (C139) SECOND ROW MODE DOOR DRIVER CIRCUIT, (C939) SECOND ROW MODE DOOR COMMON DRIVER CIRCUIT, (C255) LEFT BLEND DOOR DRIVER CIRCUIT, (C55) LEFT BLEND DOOR COMMON DRIVER CIRCUIT, (C268) RECIRCULATION DOOR DRIVER CIRCUIT, & THE (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT



Measure the resistance between the (C66) Front Mode Door Common Driver circuit and the (C139) Second Row Mode Door Driver circuit, (C939) Second Row Mode Door Common Driver circuit, (C255) Left Blend Door Driver circuit, (C55) Left Blend Door Common Driver circuit, (C268) Recirculation Door Driver circuit, and the (C68) Recirculation Door Common Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms on any of the circuits?

Yes


No

5. CHECK THE (C139) SECOND ROW MODE DOOR DRIVER CIRCUIT FOR A SHORT TO THE (C255) LEFT BLEND DOOR DRIVER CIRCUIT, (C55) LEFT BLEND DOOR COMMON DRIVER CIRCUIT, (C268) RECIRCULATION DOOR DRIVER CIRCUIT, & THE (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT



Measure the resistance between the (C139) Second Row Mode Door Driver circuit and the (C255) Left Blend Door Driver circuit, (C55) Left Blend Door Common Driver circuit, (C268) Recirculation Door Driver circuit, and the (C68) Recirculation Door Common Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms on any of the circuits?

Yes


No

6. CHECK THE (C939) SECOND ROW MODE DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO THE (C255) LEFT BLEND DOOR DRIVER CIRCUIT, (C55) LEFT BLEND DOOR COMMON DRIVER CIRCUIT, (C268) RECIRCULATION DOOR DRIVER CIRCUIT, & THE (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT



Measure the resistance between the (C939) Second Row Mode Door Common Driver circuit and (C255) Left Blend Door Driver circuit, (C55) Left Blend Door Common Driver circuit, (C268) Recirculation Door Driver circuit, and the (C68) Recirculation Door Common Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms on any of the circuits?

Yes


No

7. CHECK THE (C255) LEFT BLEND DOOR DRIVER CIRCUIT FOR A SHORT TO THE (C268) RECIRCULATION DOOR DRIVER CIRCUIT & THE (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT



Measure the resistance between the (C255) Left Blend Door Driver circuit and the (C268) Recirculation Door Driver circuit and the (C68) Recirculation Door Common Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms on any of the circuits?

Yes


No

8. CHECK THE (C55) LEFT BLEND DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO THE (C268) RECIRCULATION DOOR DRIVER CIRCUIT & THE (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT



Measure the resistance between the (C55) Left Blend Door Common Driver circuit and the (C268) Recirculation Door Driver circuit and the (C68) Recirculation Door Common Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms on any of the circuits?

Yes


No

9. CHECK THE FRONT MODE DOOR ACTUATOR CIRCUIT RESISTANCE



Measure the resistance between the (C66) Front Mode Door Common Driver Circuit and the (C266) Front Mode Door Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 30.0 ohms?

Yes


No

10. CHECK THE (C66) FRONT MODE DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO THE (C266) FRONT MODE DOOR DRIVER CIRCUIT



Disconnect the Front Mode Door Actuator harness connector.
Measure the resistance between the (C66) Front Mode Door Common Driver Circuit and the (C266) Front Mode Door Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms?

Yes


No

11. CHECK THE SECOND ROW MODE DOOR ACTUATOR CIRCUIT RESISTANCE



Measure the resistance between the (C939) Second Row Mode Door Common Driver Circuit and the (C139) Second Row Mode Door Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 30.0 ohms?

Yes


No

12. CHECK THE (C939) SECOND ROW MODE DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO THE (C139) SECOND ROW MODE DOOR DRIVER CIRCUIT



Disconnect the Second Row Mode Door Actuator harness connector.
Measure the resistance between the (C939) Second Row Mode Door Common Driver Circuit and the (C139) Second Row Mode Door Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms?

Yes


No

13. CHECK THE LEFT BLEND DOOR ACTUATOR CIRCUIT RESISTANCE



Measure the resistance between the (C55) Left Blend Door Common Driver Circuit and the (C255) Left Blend Door Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 30.0 ohms?

Yes


No

14. CHECK THE (C55) LEFT BLEND DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO THE (C255) LEFT BLEND DOOR DRIVER CIRCUIT



Disconnect the Left Blend Door Actuator harness connector.
Measure the resistance between the (C55) Left Blend Door Common Driver Circuit and the (C255) Left Blend Door Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms?

Yes


No

15. CHECK THE RECIRCULATION DOOR ACTUATOR CIRCUIT RESISTANCE



Measure the resistance between the (C68) Recirculation Door Common Driver Circuit and the (C268) Recirculation Door Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 30.0 ohms?

Yes


No

16. CHECK THE (C68) RECIRCULATION DOOR COMMON DRIVER CIRCUIT FOR A SHORT TO THE (C268) RECIRCULATION DOOR DRIVER CIRCUIT



Disconnect the Recirculation Door Actuator harness connector.
Measure the resistance between the (C68) Recirculation Door Common Driver Circuit and the (C268) Recirculation Door Driver circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10k ohms?

Yes


No

17. VERIFY THAT THE FAULT IS STILL PRESENT

Reconnect the A/C Heater Control C2 harness connector.
Turn the ignition on.
Actuate the Clear DTC function by performing the following:
Turn the ignition off, wait 10 seconds, and turn the ignition on.
Actuate the Actuator Circuit Test / Door Calibration Function by performing the following:
Actuate the Display DTC function by performing the following:

NOTE: The A/C status indicator displays active DTCs when the EBL status indicator is not illuminated and stored DTCs when the EBL status indicator is illuminated.


Read DTCs from the A/C status indicator.

Does the A/C status indicator display DTC 72?

Yes


No