B3531 - HVAC Systems - Automatic

DTC B3531

CIRCUIT DESCRIPTION
The following DTCs are for the auxiliary HVAC door actuators:
- B0145 is for the auxiliary mode actuator.
- B0428 is for the auxiliary air temperature actuator.
- B3531 is for the auxiliary console mode actuator

The auxiliary HVAC actuators are a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12 volt value to coordinate 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 one of the control circuits while providing the other with 12 volts. The auxiliary HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts. This signal then is,converted into a count value where as 1 volt will equal 51 counts.

The auxiliary HVAC control module calibrates the travel range of the HVAC door actuators when it is initially powered by the battery positive voltage circuit.

During calibration, the module commands the actuators in each direction until door travel is stopped. The module stores the minimum door positions and the maximum door positions of each actuator into memory. The total travel range is calculated by subtracting the minimum door position from the maximum door position.

CONDITIONS FOR RUNNING THE DTC
- Battery voltage is 8.7-16.5 volts.
- The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The DTC sets when one of the following conditions are present for 2 minutes:
- The actual door position value for the actuator is less than 5 counts.
- The actual door position value for the actuator is greater than 250 counts.
- The actual door position is not near the commanded door position.
- An auxiliary door actuator door position change request is made.

ACTION TAKEN WHEN THE DTC SETS
The auxiliary HVAC control module will attempt to position the actuator to its default position. They are as follows:
- B0145 defaults the auxiliary mode actuator to the floor position.
- B0428 defaults the auxiliary air temperature actuator to the full hot position.
- B3531 defaults the console mode actuator to the floor position.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
- The history DTC will clear after 100 fault free ignition cycles.
- The DTC can be cleared with a scan tool.

DIAGNOSTIC AIDS
- If the condition is not present refer to in Diagnostic Aids.
- If the DTC sets following a calibration of the door actuator, inspect the door and the actuator for the following conditions:
- A misaligned actuator
- Broken linkages or binding linkages
- A broken door or a binding door
- An obstruction that prevents the door from operating within the full range of motion
- Missing seals to the door
- Poor connections at the harness connector of the door actuator

TEST DESCRIPTION

Steps 1-5:

Steps 6-9:

Steps 10-11:

Step 12:

Steps 13-17:

Steps 18-21:

Steps 22-25:

Steps 26-31:

The numbers below refer to the step numbers on the diagnostic table.
2. If more than one DTC is set, observe all of the Door Actual parameters for each corresponding DTC. If the door actual parameter is not out of range, then the concern is with the control portion of the actuator.
7. The purpose of this step is to try to determine which actuator is internally shorted or if the auxiliary HVAC control module is creating the fault. After DTC are cleared, it can take up to 4 minutes for DTC to set.
8. After DTC are cleared, it can take up to 4 minutes for DTC to set. The purpose of this step is to try to determine which actuator is internally shorted or if the auxiliary HVAC control module is creating the fault. If both DTCs return the auxiliary control module is internally shorted.
10. The purpose of this step is to try to determine which actuator is internally shorted or if the auxiliary HVAC control module is creating the fault. After DTC are cleared, it can take up to 4 minutes for DTC to set.
11. After DTC are cleared, it can take up to 4 minutes for DTC to set. The purpose of this step is to try to determine which actuator is internally shorted or if the auxiliary HVAC control module is creating the fault. If both DTCs return the auxiliary HVAC control module is internally shorted.
14. If the scan tool does not display all three DTC, then the answer is No.
15. If the scan tool does not display both DTC, then the answer is No.
18. If the fused jumper opens, then the appropriate signal circuit is shorted to a power.
19. If the scan tool parameter reads lower than 5 Counts then the appropriate signal circuit is shorted to a ground.
20. This step tests the 5 volt reference circuit. Test can be done with any auxiliary actuator. The auxiliary air temperature actuator can be accessed the quickest.
22. If the scan tool displays one DTC when an actuator is disconnected, then the actuator that was disconnected is the area of the fault.
29. The procedure for both auxiliary mode actuators are within the same replacement procedure.
30. After a circuit repair, a recalibration of the actuators must be performed to ensure proper performance from the auxiliary HVAC system.