Circuit Description
The actuator is an electronic stepper motor. The HVAC control module (IPM) supplies power and ground to the actuator. The IPM 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 (9.5-12 volts). The IPM determines the door position by counting pulses (voltage fluctuations) caused by the brush to commutator action generated during normal motor operation. The IPM monitors a voltage drop across an internal resistance to detect the pulses. The IPM converts the pulses to counts with a range of 0-255 counts.
When a calibration or recalibration procedure is performed, the IPM calculates the door travel range. The IPM commands the actuator to each extreme position and counts the total number of pulses. The IPM 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 actuator |
| • | Temperature control 2 circuit refers to the right air temperature actuator |
| • | Temperature control 3 circuit refers to the auxiliary air temperature actuator |
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B0248 Air Flow Control 3 Circuit |
| • | DTC B0268 Air Flow Control 7 Circuit |
| • | DTC B0408 Temperature Control 1 Circuit |
| • | DTC B0423 Temperature Control 2 Circuit |
| • | DTC B0428 Temperature Control 3 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 B0249 Air Flow control 3 circuit range |
| • | DTC B0269 Air Flow control 7 circuit range |
| • | DTC B0409 Temperature control 1 circuit range |
| • | DTC B0419 Temperature control 2 circuit range |
| • | DTC B0429 Temperature control 3 circuit range |
Conditions for Setting the DTC
The IPM does not detect any movement of the actuator.
Action Taken When the DTC Sets
| • | The IPM will recalibrate the appropriate actuator each time the ignition switch is turned ON. |
| • | If DTC B0268 is set, the HVAC control module (IPM) will command the recirculation door to the outside air position. |
Conditions for Clearing the MIL/DTC
| • | The DTC will become history if the IPM 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
| • | Inspect the actuator door and actuator for the following conditions: |
| - | A misaligned actuator--Refer to Mode Actuator Replacement , Air Temperature Actuator Assembly Replacement , Air Temperature Actuator Replacement - Left Side or Recirculation Actuator Replacement . |
| - | 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 |
| • | Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step verifies that the IPM is able to command the appropriate actuator through its full range of motion.
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This step verifies that the IPM has successfully calibrated the appropriate actuator.
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If the actuator does not move at all, the problem is likely to be the drive circuitry within the IPM, 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.
-
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.
-
This step drives the actuator in the opposite direction.
Step | Action | Values | 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 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||||
Does the scan tool indicate that the value of the appropriate Actual parameter changes from the minimum specified value to the maximum specified value? | 0 Counts 255 Counts | Go to Step 3 | Go to Step 4 | |||||||||||
With a scan tool observe the appropriate Cal. Status parameter in the Instrument Panel Module data list. Does the scan tool display Cal OK? | -- | Go to Diagnostic Aids | Go to Step 8 | |||||||||||
Does the scan tool indicate that the value of the appropriate Actual parameter changes by more than the specified value? | 0-3 Counts | Go to Step 8 | Go to Step 5 | |||||||||||
5 | Test the appropriate door control A circuit and the appropriate door control B circuit for an open, high resistance, short to ground, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 6 | ||||||||||
Does the actuator shaft rotate? | -- | Go to Step 10 | Go to Step 7 | |||||||||||
Does the actuator shaft rotate? | -- | Go to Step 10 | Go to Step 8 | |||||||||||
8 | Inspect the appropriate door and actuator for the following conditions:
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 | ||||||||||
9 | Inspect for poor connections at the harness connector of the appropriate actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||||||
10 | Inspect for poor connections at the harness connector of the IPM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||||||||
11 |
Important: Perform the recalibration procedure for the appropriate actuator. Replace the appropriate actuator. Refer to following: Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
12 | Replace the IPM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||
13 |
Does the DTC reset? | -- | Go to Step 3 | System OK | ||||||||||
