B0429

CIRCUIT DESCRIPTION
The auxiliary air temperature actuator is an electronic device that incorporates a stepper motor and feedback potentiometer. The position of the auxiliary air temperature actuator is based on the auxiliary air temperature door position signal voltage from the potentiometer. The rear auxiliary HVAC module converts this voltage to a digital signal that can be transmitted over the keyboard display driver (KDD) data bus to the HVAC control module. The HVAC control module contains the logic that controls the operation of the auxiliary air temperature actuator. 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 auxiliary air temperature door and or actuator can cause this DTC to set.
- If condition not present refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-8:

Steps 9-15:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines it the auxiliary air temperature door position is within the specified range of the commanded value.
4. Tests for the proper operation of the circuit in the low voltage range.
5. Tests for the proper operation of the circuit in the high voltage range. It the jumper fuse opens when you perform this test, then the signal circuit contains a short to ground.
6. Tests for a short to voltage in the 5 volt reference circuit.