HVAC System - Manual

DTC B0248, B0408, or B0268

Circuit Description

The HVAC control module controls the HVAC actuators to regulate the airflow through the HVAC system. Each actuator is a 2-wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.

The HVAC control module determines the door position by counting motor pulses on one of the control circuits. 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 travel range. 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 limited and more that 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 driver temperature actuator.
* Temperature Control 2 Circuit refers to the passenger temperature actuator.
* Temperature Control 3 Circuit refers to the rear temperature actuator.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC B0248 05 Air Flow Control 3 Circuit short to battery or open
* DTC B0248 06 Air Flow Control 3 Circuit short to ground or open
* DTC B0248 61 Air Flow Control 3 Circuit actuator stuck
* DTC B0268 05 Air Flow Control 7 Circuit short to battery or open
* DTC B0268 06 Air Flow Control 7 Circuit short to ground or open
* DTC B0268 61 Air Flow Control 7 Circuit actuator stuck
* DTC B0408 05 Temperature Control 1 Circuit short to battery or open
* DTC B0408 06 Temperature Control 1 Circuit short to ground or open
* DTC B0408 61 Temperature Control 1 Circuit actuator stuck

Conditions for Running the DTC

The HVAC control module has completed a calibration/recalibration of the actuator.

Conditions for Setting the DTC

The HVAC control module does not detect any movement of the actuator, after 2 unsuccessful attempts at moving 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.

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 100 fault-free ignition cycles.
* The DTC can be cleared with a scan tool.

Diagnostic Aids

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

* A misaligned actuator
* Broken or binding linkages or actuator door
* Obstruction that prevents the 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:

The numbers below refer to the step numbers on the diagnostic table.
3. This step drives the actuator in one direction. The actuator shaft will not move if the actuator door is already in the position you are attempting to drive it to.
4. This step drives the actuator in the opposite direction.