B3531

DTC B3531

CIRCUIT DESCRIPTION
The following DTCs are for the HVAC door actuators:
- B0429 is for the auxiliary air temperature actuator.
- B3531 is for the auxiliary mode actuator.

The auxiliary HVAC control module controls the auxiliary HVAC door actuators to regulate the airflow through the auxiliary HVAC system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The logic circuit inside the actuators receives control signals from the auxiliary HVAC control module and controls the internal stepper motor. When a door positional change is required, the auxiliary HVAC control module calculates a commanded door position. The module compares the commanded door position to the actual door position and determines the needed direction of motor rotation. The module applies a signal voltage to the door control circuit that is an input to the internal logic circuit of the door actuator. A 5-volt signal increases the door position. A 0 volt signal decreases the door position. When the commanded door position is equal to the actual door position, the auxiliary HVAC control module sends a 2.5-volt signal to the door actuator and motor rotation stops. The ignition 3 voltage circuit provides source voltage to the logic circuit. The module provides ground to the actuator logic circuit through the low reference circuit.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC B0429 Temperature Control 3 Circuit Range/Performance
- DTC B3531 Air Flow Control 10 Circuit

CONDITIONS FOR RUNNING THE DTC
- Source voltage is 8.7-16.5 volts.
- The ignition is ON.
- The auxiliary HVAC control module commands the actuator to move.

CONDITIONS FOR SETTING THE DTC
The actual door position is not near the commanded door position

ACTION TAKEN WHEN THE DTC SETS
The auxiliary HVAC control module does not command the actuator to move for the remainder of the ignition cycle.

CONDITIONS FOR CLEARING THE DTC
- The DTC becomes history during the next ignition cycle in which the auxiliary HVAC control module no longer detects a stall condition.
- 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 Testing for Intermittent Conditions and Poor Connections in Diagnostic Aids.
- Inspect the appropriate door and door actuator for the following conditions:
- A misaligned door actuator
- A binding door
- An obstruction that prevents the door actuator from operating within the full range of motion

TEST DESCRIPTION

Steps 1-9:

Steps 10-13:

The numbers below refer to the step numbers on the diagnostic table.
2. Determines if the auxiliary HVAC door actuator is stalled.
3. Applies control circuit voltages to the input of the auxiliary HVAC door actuator.