B0252

DTC B0252

CIRCUIT DESCRIPTION
The following DTC's 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 potentiometer's adjustable contact changes the door position signal between 0-5 volts. The IPM converts the voltage values to count values where 1 V 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.

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC
- Left air temperature actuator
- Mode actuator
- Right air temperature actuator
- Recirculation actuator

ACTION TAKEN WHEN THE DTC SETS
- A default value will be substituted for the door position data by the IPM.
- Each time the ignition switch is turned ON, the IPM will recheck the actuator travel range.
- The IPM will continue to make use of whatever travel range is still available.
- If B0252 or 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.

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 cycles.
- The DTC can be cleared with a scan tool.

DIAGNOSTIC AIDS
- If the condition is not present, refer to Diagnostic Aids for Circuit Testing and Wiring Repair procedures.
- The range fault can only be detected following a check of the actuator travel range. The actuator travel range check can only be initiated by disrupting power to the IPM.
- An actual range below this limit suggest an obstruction or something stuck in the door limiting travel. An actual range above this limit suggests an over travel condition such as damaged or missing foam seal.
- A damaged or broken door an or actuator can cause the DTC to set by allowing the actuator shaft to rotate unrestricted to its internal stop. The internal stops are outside of the working range of the feedback potentiometers 0-250 count.
- Left air temperature actuator
The calibration limit is 152-220 counts.
- Mode actuator
The calibration limit is 200-246 counts.
- Recirculation actuator
The calibration limit is 149-220 counts.
- Right air temperature actuator
The calibration limit is 147-220 counts.

TEST DESCRIPTION

Steps 1 - 3:

Steps 4 - 5:

Steps 6 - 10:

Steps 11 - 17:

The numbers below refer to the step numbers on the diagnostic table.
2. Tests for the HVAC actuator operating within its travel range.
3. Test the actual travel range of the HVAC actuator.
4. Tests the HVAC actuator for proper operation.
5. 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 is shorted to voltage.
6. Tests for the proper operation of the circuit in the high voltage range.
7. 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.
8. Tests for a short in the 5 volt reference circuit.
11. Tests the HVAC actuator door position signal circuit for a short to ground.
12. Tests the HVAC actuator door position signal circuit for a short to voltage, high resistance, or an open.
13. Tests the HVAC actuator low reference circuit for high resistance or an open.
14. Tests the HVAC actuator ignition 3 voltage circuit for high resistance or an open.
15. Tests the HVAC actuator door control circuit for an open, high resistance, or a short to ground.
16. Test for an inoperative HVAC actuator.
17. Tests for proper operation of the IPM.