Diagnostic Instructions

DTC Descriptors

DTC B0238: Air Flow Control 1 Defrost Circuit-- Defrost Actuator

DTC B0239: Air Flow Control 1 Defrost Circuit Range/Performance-- Auxiliary Mode Actuator

DTC B0248: Air Flow Control 3 Blend Defog and Floor Circuit-- Mode Actuator

DTC B0249: Air Flow Control 3 Blend Defog and Floor Circuit Range/Performance-- Mode Actuator

DTC B0250: Air Flow Control 3 Blend Defog and Floor Circuit Low-- Defrost Actuator

DTC B0268: Air Flow Control 7 Recirculate Circuit-- Recirculation Actuator

DTC B0269: Air Flow Control 7 Recirculate Circuit Range/Performance-- Recirculation Actuator

DTC B0408: Temperature Control Left Circuit-- Left Temperature Actuator

DTC B0409: Temperature Control Left Circuit Range/Performance-- Left Temperature Actuator

DTC B0414: Temperature Control Left Feedback Circuit Range/Performance-- Left Temperature Actuator

DTC B0418: Temperature Control 2 Passenger Circuit-- Right Temperature Actuator

DTC B0419: Temperature Control 2 Passenger Circuit Range/Performance-- Right Temperature Actuator

DTC B0424: Temperature Control 2 Passenger Feedback Circuit Range/Performance-- Right Temperature Actuator

DTC B0428: Temperature Control 3 Rear Circuit-- Auxiliary Temperature Actuator

DTC B0429: Temperature Control 3 Rear Circuit Range/Performance-- Auxiliary Temperature Actuator

DTC B0434: Temperature Control 3 Rear Feedback Circuit Range/Performance-- Auxiliary Temperature Actuator

DTC B3532: Air Flow Control 10 Rear Circuit Range/Performance-- Auxiliary Mode Actuator

DTC B3747: Air Flow Control 1 Defrost Feedback Circuit Range/Performance-- Defrost Actuator

DTC B3748: Air Flow Control 3 Blend Defog and Floor Feedback Circuit Range/Performance-- Mode Actuator

DTC B3749: Air Flow Control 7 Recirculate Feedback Circuit Range/Performance-- Recirculation Actuator

DTC B3782: Air Flow Control 10 Rear Feedback Circuit-- Auxiliary Mode Actuator

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Vent and Floor Door Control	B0248, B0249, B0251, B3748, B3761	B0248, B0249, B0251, B3748, B3761	B0248, B0249, B0251, B3748, B3761	--
Defrost Door Control	B0238, B0239, B3747	B0238, B0239, B3747	B0238, B0239, B3747	--
Recirculation Door Control	B0268, B0269, B3749	B0268, B0269, B3749	B0268, B0269, B3749	--
Left Air Temperature Door Control	B0408, B0409, B0414	B0408, B0409, B0414	B0408, B0409, B0414	--
Right Air Temperature Door Control	B0418, B0419, B0424	B0418, B0419, B0424	B0418, B0419, B0424	--
Auxiliary Mode Door Control	B3531, B3532, B3782	B3531, B3532, B3782	B3531, B3532, B3782	--
Auxiliary Air Temperature Door Control	B0428, B0429, B0434	B0428, B0429, B0434	B0428, B0429, B0434	--

Circuit/System Description

The HVAC control module controls the HVAC actuators to regulate the airflow and temperature through the HVAC system. The actuators are 2-wire, bi-directional electric motors that share the same common control circuit. When the operator adjusts the actuators, the control module can only operate one actuator at a time due to the shared common control circuit. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.

The HVAC control module determines the door position by counting motor pulses on one of the control circuits. The HVAC control module converts the pulses to counts with a range of 0-255 counts.

When a calibration or recalibration procedure is performed, the HVAC control module calculates the door travel range. The HVAC control module compares the total number of pulses to calibrated limits. If the total pulse count is less than or equal to the maximum calibrated limited and more than or equal to the minimum calibrated limit, then the calibration is considered successful.

Conditions for Running the DTC

Conditions for Setting the DTC

The actual door position differs from the commanded door position by more than 4 counts or the HVAC control module detects the door position signal circuit is less than 7 counts or greater than 250 counts.

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Diagnostic Aids

Inspect the appropriate actuator door for the following conditions:

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Verification

Ignition ON, observe the operation of the drive shaft of the appropriate actuator while using the appropriate control switch. The drive shaft of the actuator should rotate.

Circuit/System Testing

1. Ignition OFF, disconnect harness connector at the appropriate actuator.
2. Verify the appropriate scan tool parameter is less than 4 counts.

⇒	If greater than 4 counts, test the control circuit for a short to ground. If the circuit tests normal, replace the HVAC control module

3. Install a 3-amp fused jumper wire between the appropriate actuator control circuit terminal 1 and the common door control circuit terminal 6. Verify the appropriate scan tool parameter is greater than 250 counts.

⇒	If less than 250 counts, test the actuator control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

4. If all circuits test normal, replace the actuator.

Component Testing

1. Install a 10-amp fused jumper wire between the control terminal 1 and 12 volts. Momentarily install a jumper wire between the common door control terminal 6 and ground. The appropriate actuator shaft should rotate.

⇒	If the function does not perform as specified, replace the appropriate actuator.

2. Reverse the jumper wires; the appropriate actuator shaft should rotate.

⇒	If the function does not perform as specified, replace the appropriate actuator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.