Circuit Description
The HVAC control module controls the HVAC actuators to regulate the airflow and temperature through the HVAC system. The actuators are 2-wire, bi-directional electric motors that share the same common control circuit. When the operator adjusts the actuators, the control module can only operate one actuator at a time due to the shared common control circuit. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. 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 than or equal to the minimum calibrated limit, then the calibration is considered successful.
| • | Air Flow Control 1 refers to the defrost actuator. |
| • | Air Flow Control 3 refers to the mode actuator. |
| • | Air Flow Control 7 refers to the recirculation actuator. |
| • | Air Flow Control 10 refers to the auxiliary mode actuator. |
| • | Temperature Control refers to the left air temperature actuator. |
| • | Temperature Control 2 refers to the right air temperature actuator. |
| • | Temperature Control 3 refers to the auxiliary air temperature actuator. |
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B0238 Air Flow Control 1 Circuit |
| • | DTC B0239 Air Flow Control 1 Circuit Performance |
| • | DTC B0248 Air Flow Control 3 Circuit |
| • | DTC B0249 Air Flow Control 3 Circuit Performance |
| • | DTC B0251 Air Flow Control 3 Circuit Feedback Circuit Performance |
| • | DTC B0268 Air Flow Control 7 Circuit |
| • | DTC B0269 Air Flow Control 7 Circuit Performance |
| • | DTC B0408 Temperature Control Circuit |
| • | DTC B0409 Temperature Control Circuit Performance |
| • | DTC B0414 Temperature Control Feedback Circuit Performance |
| • | DTC B0418 Temperature Control 2 Circuit |
| • | DTC B0419 Temperature Control 2 Circuit Performance |
| • | DTC B0424 Temperature Control 2 Feedback Circuit Performance |
| • | DTC B0428 Temperature Control 3 Circuit |
| • | DTC B0429 Temperature Control 3 Circuit Performance |
| • | DTC B0434 Temperature Control 3 Feedback Circuit Performance |
| • | DTC B3531 Air Flow Control 10 Circuit |
| • | DTC B3532 Air Flow Control 10 Circuit Performance |
| • | DTC B3747 Air Flow Control 1 Feedback Circuit |
| • | DTC B3749 Air Flow Control 7 Feedback Circuit Performance |
| • | DTC B3782 Air Flow Control 10 Feedback Circuit Performance |
Conditions for Running the DTC
The HVAC control module has completed 2 calibration/recalibration events of the actuators.
Action Taken When the DTC Sets
| • | The HVAC control module will substitute a default range value. |
| • | The HVAC control module will no longer issue commands to the actuator if its run timer expires during the calibration/recalibration event. |
The HVAC control module will substitute a default range value.
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--Refer to the following procedures: |
| - | 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
The numbers below refer to the step numbers on the diagnostic table.
-
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.
-
This step drives the actuator in the opposite direction.
Step | Action | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | |||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||||||||
2 | Test the appropriate door control circuit and the common door control circuit for an open, high resistance, short to ground, or a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 3 | ||||||||||
Does the actuator shaft rotate? | Go to Step 7 | Go to Step 4 | |||||||||||
Does the actuator shaft rotate? | Go to Step 7 | Go to Step 5 | |||||||||||
5 | Inspect the appropriate door and actuator for the following conditions:
Did you find and correct the condition? | Go to Step 10 | Go to Step 6 | ||||||||||
6 | Inspect for poor connections at the harness connector of the appropriate actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 8 | ||||||||||
7 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 10 | Go to Step 9 | ||||||||||
8 | Replace the appropriate actuator. Refer to the following: Did you complete the replacement? | Go to Step 10 | -- | ||||||||||
9 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 10 | -- | ||||||||||
10 |
Does the DTC reset? | Go to Step 2 | System OK | ||||||||||
