B0423

CIRCUIT DESCRIPTION
The right air temperature actuator is an electronic stepper motor that is part of the air temperature actuator assembly. The HVAC control module supplies power and ground to the actuator. The HVAC control module controls the direction of the right air temperature actuator by changing the polarity of the control circuits. When the actuator reaches its desired position both circuits are fixed to the same value (9.5 to 12 volts). The HVAC control module determines the door position by counting pulses (voltage fluctuations) caused by the brush to commutator action generated during normal motor operation. The HVAC control module (IPM) monitors a voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0 to 255 counts.

When a calibration or recalibration procedure is performed, the HVAC control module calculates the right air temperature door travel range. The HVAC control module commands the actuator to each extreme position and counts the total number of pulses. The HVAC control module compares the total number of pulses to calibrated limits. If the total pulse count is less than or equal to the maximum calibrated limit and greater than or equal to the minimum calibrated limit, then the calibration is considered successful.

CONDITIONS FOR RUNNING THE DTC
This DTC runs during and after the next range check following the setting of DTC B0419.

CONDITIONS FOR SETTING THE DTC
The HVAC control module does not detect any movement of the right air temperature actuator.

ACTION TAKEN WHEN THE DTC SETS
The HVAC control module will recalibrate the right air temperature actuator each time the ignition switch is turned ON.

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 condition not present refer to Testing for Intermittent and Poor Connections in Diagrams.
^ Inspect the right air temperature door and the air temperature actuator assembly for the following conditions:
- A misaligned air temperature actuator assembly. Refer to Air Temperature Actuator Assembly Replacement.
- Broken or binding linkages or right air temperature door
- An obstruction that prevents the right air temperature door from operating within it's full range of motion
- Missing seals to the right air temperature door
- Misaligned seals to the right air temperature door

TEST DESCRIPTION

Steps 1-8:

Steps 9-13:

The numbers below refer to the step numbers on the diagnostic table.
2. This step verifies that the HVAC control module is able to command the right air temperature actuator through its full range of motion.
3. This step verifies that the HVAC control module has successfully calibrated the right air temperature actuator.
4. If the actuator does not move at all, the problem is likely to be the drive circuitry within the HVAC control module, the actuator, or the wiring harness. If the actuator does move, but not within its full range of motion, the problem is likely to be a mechanical binding of the right air temperature door or right air temperature door linkage.
6. This step drives the actuator to the cold position. The right air temperature actuator will not move if the right air temperature door is in already at the extreme position.
7. This step drives the actuator to the hot position.