Manufacturer Code Charts: 4

HVAC DTC Troubleshooting: 4

DTC indicator 4:

An Open or Short in the Mode Control Motor Circuit

1. Turn the ignition switch to LOCK (0), and then back to ON (II).

2. Do the self-diagnostic function with the HVAC control unit How To Troubleshoot The Heating And A/C Systems (Without Climate Control).

3. Check for DTCs.

Is DTC 4 indicated?

YES -

Go to step 4.

NO -

Intermittent failure. Check for loose wires or poor connections on the mode control motor circuit.�

4. Turn the ignition switch to LOCK (0).

5. Test the mode control motor Mode Control Motor Test.

Is the mode control motor OK?

YES -

Go to step 6.

NO -

Replace the mode control motor Mode Control Motor Replacement.�

6. Disconnect the mode control motor 7P connector.

7. Disconnect the HVAC control unit 28P connector.

8. Check for continuity between the following terminals of the HVAC control unit 28P connector and the mode control motor 7P connector.









Is there continuity?

YES -

Go to step 9.

NO -

Repair an open in the wire(s) between the HVAC control unit and the mode control motor.�

9. Check for continuity between body ground and the HVAC control unit 28P connector terminals No. 3, 4, 5, and No. 7 individually.





Is there continuity?

YES -

Repair a short to body ground in the wire(s) between the HVAC control unit and the mode control motor.�

NO -

Go to step 10.

10. Check for continuity between the HVAC control unit 28P connector terminals as follows.





Is there continuity between any of the terminals?

YES -

Repair a short in the wires between the HVAC control unit and the mode control motor.�

NO -

Go to step 11.

11. Turn the ignition switch to ON (II), and measure the voltage between body ground and the HVAC control unit 28P connector terminals No. 3, 4, 5 and No. 7 individually.





Is there any voltage?

YES -

Repair a short to power in the wire(s) between the HVAC control unit and the mode control motor. This short may also damage the HVAC control unit. Repair the short to power before replacing the HVAC control unit HVAC Control Unit Removal/Installation (Without Climate Control).�

NO -

Check for loose wires or poor connections at the HVAC control unit 28P connector and at the mode control motor 7P connector. If the connections are good, substitute a known-good HVAC control unit, and recheck. If the symptom/indication goes away, replace the original HVAC control unit HVAC Control Unit Removal/Installation (Without Climate Control).�