Circuit Description
The following DTCs are for the HVAC door actuators:
| • | B0237 - Left Air Temperature Actuator |
| • | B0252 - Mode Actuator |
| • | B0272 - Recirculation Actuator |
| • | B0282 - Right Air Temperature Actuator |
The instrument panel module (IPM) controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference, control, 5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5, or 5 volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts. The IPM converts the voltage values to count values where 1 volt is approximately equal to 51 counts. The IPM uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded or targeted value, the control signal is changed to either 0 or 5 volts, depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates, the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.
The IPM will perform a continuous test on the current feedback voltage. If the feedback voltage does not equal or fall within the calibrated limits, the DTC will set.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B0237 Air Flow Control (general or single control) Circuit Open |
| • | DTC B0252 Air Flow Control 3 (blend defog and floor) Circuit Open |
| • | DTC B0272 Air Flow Control 7 (recirculate) Circuit Open |
| • | DTC B0282 Air Flow Control 9 (dual zone) Circuit Open |
Conditions for Running the DTC
The ignition is turned ON.
Conditions for Setting the DTC
| • | Left air temperature actuator |
| The IPM detects the signal circuit is less than 0.05 volt (3 counts) or more than 4.90 volts (250 counts). |
| • | Mode actuator |
| The IPM detects the signal circuit is less than 0.1 volt (5 counts) or more than 4.90 volts (250 counts). |
| • | Recirculation actuator |
| The IPM detects the signal circuit is less than 0.1 volt (5 counts) or more than 4.90 volts (250 counts). |
| • | Right air temperature actuator |
| The IPM detects the signal circuit is less than 0.09 volt (5 counts) or more than 4.90 volts (250 counts). |
Action Taken When the DTC Sets
| • | Left air temperature actuator |
| - | A default value of 2.50 volts (128 counts) will be substituted for the left air temperature door position data by the IPM. |
| - | The IPM will toggle the actuator between full hot and full cold in an attempt to maintain the selected air temperature on the HVAC control module. |
| • | Mode actuator |
| - | The IPM will only direct airflow from either the vent or defrost outlets. |
| - | If B0252 sets during a calibration/recalibration event, the IPM will no longer issue commands to the actuator and will not perform a calibration/recalibration until the door position feedback fault is corrected. |
| • | Recirculation actuator |
| - | The recirculation actuator will be set to the outside air position. |
| - | If B0272 sets during a calibration/recalibration event, the IPM will no longer issue commands to the actuator and will not perform a calibration/recalibration until the door position feedback fault is corrected. |
| • | Right air temperature actuator |
| - | A default value of 2.50 volts (128 counts) will be substituted for the right air temperature door position data by the IPM. |
| - | The IPM will toggle the actuator between full hot and full cold in an attempt to maintain the selected air temperature on the HVAC control module. |
Conditions for Clearing the 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
| • | If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | A disconnected or broken door/linkage may also set this DTC during calibration/recalibration by allowing the actuator to travel to its minimum internal stops, creating an over travel condition. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step tests for the HVAC actuator operating within its travel range.
-
This step tests the HVAC actuator for proper operation.
-
This step tests for the proper operation of the circuit in the high voltage range.
-
This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
-
This step tests for a short to ground in the 5-volt reference circuit.
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 appropriate Dr Actual parameter is within the specified range? |
| Go to Diagnostic Aids | Go to Step 3 | |||||||||
Does the scan tool indicate that the appropriate Dr Actual parameter changes when the appropriate door position is commanded? |
| Go to Step 12 | Go to Step 4 | |||||||||
Does the scan tool indicate that the appropriate Dr Actual parameter is more than the specified value? | 4.90 V | Go to Step 5 | Go to Step 9 | |||||||||
Does the scan tool indicate that the appropriate Dr Actual parameter is less than the specified value? |
| Go to Step 6 | Go to Step 10 | |||||||||
Does the scan tool indicate that the appropriate Dr Actual parameter is more than the specified value? | 4.90 V | Go to Step 8 | Go to Step 7 | |||||||||
7 | Test the 5-volt reference circuit of the appropriate HVAC actuator for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 | ||||||||
8 | Test the 5-volt reference circuit for the following:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 13 | ||||||||
9 | Test the door position signal circuit of the appropriate HVAC actuator for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 | ||||||||
10 | Test the door position signal circuit of the appropriate HVAC actuator for the following:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 11 | ||||||||
11 | Test the low reference circuit for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 | ||||||||
12 | Inspect the appropriate HVAC door for a condition allowing excessive travel of the actuator. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 13 | ||||||||
13 | Inspect for poor connections at the harness connector of the appropriate HVAC 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 17 | Go to Step 15 | ||||||||
14 | 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 17 | Go to Step 16 | ||||||||
15 | Replace the HVAC door actuator. Refer to the appropriate replacement procedure: Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||||
16 | 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 17 | -- | ||||||||
17 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||||
