B0414

DTC B0414, B0424, B3748, or B3749

Circuit Description

The actuator is an electronic stepper motor. The HVAC control module supplies power and ground to the actuator. The HVAC control module controls the direction of the actuator by changing the polarity of the control circuits. When the actuator reaches its desired position, both circuits are fixed to the same value 0 volts. The HVAC control module determines the door or mode film position by counting pulses, voltage fluctuations, caused by the brush to commutator action generated during normal motor operation. The HVAC control module 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 0-255 counts.

When a calibration or recalibration procedure is performed, the HVAC control module calculates the door or mode film travel range. The HVAC control module commands the actuator in one extreme position then counts pulses starting from 0 counts. 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.

* Air flow control 3 circuit refers to the mode actuator.
* Air flow control 7 circuit refers to the recirculation actuator.
* Temperature control 1 circuit refers to the left air temperature.
* Temperature control 2 circuit refers to the right air temperature.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC B0414 Air Flow Control 3 Circuit
* DTC B0424 Air Flow Control 7 Circuit
* DTC B3748 Temperature Control 1 Circuit
* DTC B3749 Temperature Control 2 Circuit

Conditions for Running the DTC

The ignition is turned ON. The inoperative actuator DTC runs during and after the next range check following the setting of the actuator range error DTC. The appropriate actuator inoperative code will set with the appropriate actuator range error code.

* DTC B0414 Air Flow Control 3 Circuit Range
* DTC B0424 Air Flow Control 7 Circuit Range
* DTC B3748 Temperature Control 1 Circuit Range
* DTC B3749 Temperature Control 2 Circuit Range

Conditions for Setting the DTC

The HVAC control module does not detect any movement of the actuator.

Action Taken When the DTC Sets

* The HVAC control module will recalibrate the appropriate actuator each time the ignition switch is turned ON.
* If DTC B0424 is set, the HVAC control module will command the recirculation door to the outside air position.

Conditions for Clearing the MIL/DTC

* The DTC will become history if the HVAC control module no longer detects a failure.
* The history DTC will clear after 100 fault-free ignition cycles.
* The DTC can be cleared with a scan tool.

Diagnostic Aids

* Inspect the actuator door and actuator for the following conditions:

- A misaligned actuator-Refer to Mode Actuator Replacement, Air Temperature Actuator Replacement - Right, Air Temperature Actuator Replacement - Left or Recirculation Actuator Replacement.
- Broken or binding mode actuator film or actuator door
- Obstruction that prevents the mode film or actuator door from operating within its full range of motion
- Missing seals to the actuator door
- Misaligned seals to the actuator door

Test Description

Step 1 - Step 9:

Step 10 - Step 12:

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 appropriate actuator through its full range of motion.
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 actuator door or actuator door linkage.
6. This step drives the actuator in one position. The actuator shaft will not move if the actuator door is already in the position you are attempting to drive it to.
7. This step drives the actuator in the opposite direction.