B0363

CIRCUIT DESCRIPTION
The following DTCs are for the HVAC door actuators:
- B0363 - left air temperature actuator
- B0367 - right air temperature actuator

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference, control, 5 volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5 volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5 volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts. The HVAC control module converts the voltage values to count values where 1 V is approximately equal to 51 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC
The air temperature door signal circuit stays at 4.5 volts or higher.

ACTION TAKEN WHEN THE DTC SETS
No driver warning message will be displayed for this DTC.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the HVAC control module no longer detects a failure.
- The history DTC will clear after 50 fault-free ignition cycles.
- The DTC can be cleared with a scan tool.

DIAGNOSTIC AIDS
If the condition is not present, refer to Diagnostic Aids for circuit testing and wiring repair procedures.

TEST DESCRIPTION

Steps 1-5:

Steps 6-8:

Steps 9-13:

The numbers below refer to the step numbers on the diagnostic table.
3. This step checks for a default action by the actuator. The actuator will default to 128 counts if the air temperature door position circuit is open, shorted to ground, or shorted to voltage. It will also default to this value if the low reference circuit or the 5 volt reference circuit is open.
4. Tests for the air temperature actuator operating within its specified range.
5. Tests the air temperature actuator ground circuit for an open.
6. Tests the air temperature actuator 5 volt reference circuit for a short to ground, short to voltage, or an open.
7. Tests the air temperature door position signal circuit for an open, high resistance, short to ground, or short to voltage.