A/C Control Mode Door Input Open Or Shorted To Battery (Manual A/C)

NOTE: After making any repairs, perform BODY VERIFICATION TEST under VERIFICATION TESTS.

Monitored & Set Condition

When Monitored: With the ignition on.
Set Condition: The BCM detects an abnormally high voltage on its mode request input.

Possible Causes:

Testing

With the scan tool, erase BODY CONTROL DTC's. Turn ignition off. Disconnect manual temp control head C1 harness connector. See Figure . Disconnect the BCM C2 harness connector. See Figure . Turn ignition on. Measure the voltage of the mode switch MUX circuit. If there is any voltage present, repair the mode switch MUX circuit for a short to voltage. If there is not any voltage, go to next step.
Turn ignition off. Measure the resistance of the mode switch MUX circuit between the manual temperature control head C1 connector and the BCM C2 connector. If the resistance is 5 ohms or less, go to next step. If the resistance is 5 ohms or more, repair the mode switch MUX circuit for an open.
Reconnect the BCM C2 harness connector. Turn the ignition on. Measure the voltage of the mode switch MUX circuit. If the voltage is 4.9 volts or more, replace the control head. See MANUAL A/C-HEATER SYSTEMS - CONCORDE & INTREPID article in HVAC. If the voltage is 4.9 volts or less, replace the BCM. See BODY CONTROL MODULE under REMOVAL & INSTALLATION.