Diagnostic Instructions

DTC Descriptors

DTC B0248 : Air Flow Control 3 Circuit

DTC B0263 : Air Flow Control 6 Circuit

DTC B0408: Temperature Control 1 Circuit

DTC B0414 : Range/Performance Temperature Control 2 Feedback Circuit

DTC B0418: Temperature Control 2 Circuit

DTC B0424 :  Range/Performance

DTC B3761 : Air Flow Control 3 Feedback Circuit

DTC B3770 : Air Flow Control 6 Feedback Circuit

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Driver Air Temperature 5-Volt Reference Circuit	B0229, B0414, B0424, B3761, B3770, B0248, B0263, B0268, B0408 or B0418	B0414	B0229, B0414, B0424, B3761, B3770, B0248, B0263, B0268, B0408 or B0418	B0414
Driver Air Temperature Door Position Signal	B0414	B0414	B0414	B0414
Driver Air Temperature Door Control Circuit	B0414	B0414	B0414	--
Driver Air Temperature Door Voltage Supply Circuit	--	B0414	--	--
Driver Air Temperature Low Reference Circuit	--	B0413 05	--	--
Passenger Air Temperature 5-Volt Reference Circuit	B0229, B0414, B0424, B3761, B3770, B0248, B0263, B0268, B0408 or B0418	B0424	B0229, B0414, B0424, B3761, B3770, B0248, B0263, B0268, B0408 or B0418	B0424
Passenger Air Temperature Door Position Signal	B0424	B0424	B0424	B0424
Passenger Air Temperature Door Control Circuit	B0424	B0424	B0424	B0424
Passenger Air Temperature Door Voltage Supply Circuit	--	B0424	--	--
Passenger Air Temperature Low Reference Circuit	--	B0424	--	--
Mode 5-Volt Reference Circuit	B0229, B0414, B0424, B3761, B3770, B0248, B0263, B0268, B0408 or B0418	B3770	B0229, B0414, B0424, B3761, B3770, B0248, B0263, B0268, B0408 or B0418	B3770
Mode Door Position Signal	B3770	B3770	B3770	B3770
Mode Door Control Circuit	B3770	B3770	B3770	B3770
Mode Door Supply Voltage Circuit	--	B3770	--	--
Mode Low Reference Circuit	--	B3770	--	--

Circuit/System Description

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 5-volt reference source voltage to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes. 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.

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 3 counts or greater than 253 counts.

Action Taken When the DTC Sets

The control circuit is 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 Verification

Ignition ON, command the appropriate actuator in both directions with a scan tool. The scan tool door position parameter reading should be between 3 and 253 counts.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.

4. Verify the appropriate scan tool parameter is less than 4 counts.

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

5. Install a 3-amp fused jumper wire between the signal circuit and the low reference circuit terminal. Verify the appropriate scan tool parameter is greater than 250 counts.

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

6. Ignition ON, verify that a test lamp illuminates between the ignition 3 circuit and ground.

⇒	If the test lamp does not illuminate, test the ignition 3 circuit for a short to ground an open/high resistance.

7. Install a DMM between the actuator control circuit and ground. While monitoring the DMM use the scan tool to command the appropriate actuator from one direction to the other. If the voltage on the control circuit should move from 0 volts in one direction to 5 volts in the other direction and 2.5 volts in the at rest state.

⇒	If the voltage does not change, test the control circuit for an open, short to voltage or short to ground. If circuit tests normal replace the HVAC control module.

8. If all circuits test normal, test or replace the actuator.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.