B0408

Steps 1-5:

Steps 6-13:

CIRCUIT DESCRIPTION
The air temperature actuator is an electronic device that incorporates a stepper motor and feedback potentiometer. The HVAC control module determines the position of the air temperature actuator based on the voltage from the potentiometer. When a change in air temperature is required (greater than 4 counts) the HVAC control module will drive the air temperature actuator in the appropriate direction to achieve the desired setting while comparing the actual position to the commanded position. If the actual value differs from the commanded value by 4 or more counts, the actuator is considered stalled and the DTC will set.

CONDITIONS FOR RUNNING THE DTC
- The ignition is ON.
- Ignition voltage is between 9-16 Volts.
- An actuator positional change is attempted.

CONDITIONS FOR SETTING THE DTC
The actual air mix door position differs from the commanded air mix door position by 4 counts or more.

ACTION TAKEN WHEN THE DTC SETS
The actuator is considered stalled and the HVAC control module will command the actuator to stop rotation (2.5 V).

CONDITIONS FOR CLEARING THE DTC
- If the HVAC control no longer detects a failure, then the DTC will become history.
- The history DTC will clear after 50 ignition cycles without a failure.
- The DTC can be cleared with a scan tool.

DIAGNOSTIC AIDS
- A dead zone exists in a range 10 counts above or below the mix door max or mix door mm positions. When the air mix door actual data parameter is within the dead zone, the DTC will not set. If the air mix door commanded data parameter differs from the air mix door actual data parameter by 4 counts or more outside the dead zone, the DTC will set.
- A damaged or broken air temperature door and or actuator can cause this DTC to set.
- If none of the above conditions exist refer to Testing for Intermittent and Poor Connections in diagrams.