Diagnostic Instructions

DTC Descriptors

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

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

DTC B0268: Air Flow Control 7 Recirculate Circuit

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

DTC B0408: Temperature Control 1 Circuit

DTC B0409: Temperature Control 1 Circuit Range/Performance

DTC B0414: Temperature Control 1 Feedback Circuit Range/Performance

DTC B0418: Temperature Control 2 Circuit

DTC B0419: Temperature Control 2 Circuit Range/Performance

DTC B0424: Temperature Control 2 Feedback Circuit Range/Performance

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

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

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Recirculation Door Control A	B0268, B0269, B3749	B0268, B0269, B3749	B0268, B0269, B3749	--
Recirculation Door Control B	B0268, B0269, B3749	B0268, B0269, B3749	B0268, B0269, B3749	--
Left Air Temperature Door Control A	B0408, B0409, B0414	B0408, B0409, B0414	B0408, B0409, B0414	--
Left Air Temperature Door Control B	B0408, B0409, B0414	B0408, B0409, B0414	B0408, B0409, B0414	--
Right Air Temperature Door Control A	B0418, B0419, B0424	B0418, B0419, B0424	B0418, B0419, B0424	--
Right Air Temperature Door Control B	B0418, B0419, B0424	B0418, B0419, B0424	B0418, B0419, B0424	--
Mode Door Control A	B0248, B0249, B3748	B0248, B0249, B3748	B0248, B0249, B3748	--
Mode Door Control B	B0248, B0249, B3748	B0248, B0249, B3748	B0248, B0249, B3748	--

Circuit/System Description

The actuator is an electronic stepper motor. The HVAC control module supplies power and ground to the actuator. The HVAC control module controls the direction of the actuator by changing the polarity of the control circuits. When the actuator reaches its desired position, both circuits are fixed to the same value 0 volts. The HVAC control module determines the door or mode film position by counting pulses, voltage fluctuations, caused by the brush to commutator action generated during normal motor operation. The HVAC control module monitors a voltage drop across an internal resistance to detect the pulses. 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 or mode film travel range. The HVAC control module commands the actuator in one extreme position then counts pulses starting from 0 counts. 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 limit and greater 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

Driver A and driver B circuits are deactivated for the appropriate actuator.

Conditions for Clearing the DTC

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 Testing

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
2. Ignition ON, connect a test lamp between the control circuit terminal A and control circuit terminal B. Command the actuator in each direction. The test lamp should briefly illuminate when commanding the actuator in one direction to the other direction.

⇒	If the test lamp is always OFF, test the appropriate control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

⇒	If the test lamp continuously illuminates, test the appropriate control circuit for a short to B+. If the circuit tests normal, replace the HVAC control module.

3. If all circuits test normal, replace the appropriate actuator.

Component Testing

1. Install a 10-amp fused jumper wire between the control terminal A and 12 volts. Momentarily install a jumper wire between the control terminal B 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.