When Monitored And Set Condition:

When Monitored: With the ignition on.

Set Condition: The A/C - Heater Control provides a 5 volt pull-up to the mode request selector. The BCM reads the signal from the A/C - Heater Control mode request and positions the mode door accordingly. If the voltage on this pin is below 0.1 volts, the DTC will set, and the BCM will place the mode door in a default position.