• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

For symptom byte information, refer to Symptom Byte List.

Doors in the HVAC case assembly are used to control air flow. The HVAC control module operates the doors through the use of actuators, with one actuator being used for each door. Each actuator is a 5–wire stepper motor.

With the switches and dials on the HVAC controls, air temperature door position, mode door position and recirculation door position can be selected. The selected values are passed to the HVAC control module via serial data.

The HVAC control module supplies a 12 V reference voltage to the stepper motors and energizes the 4 stepper motor control circuits with a pulsed ground signal. The stepper motors move the appropriate doors into the calculated positions, in order to reach the selected setting.

• Ignition ON.
• The HVAC control module is ON.

The stepper motors supply output is shorted to ground.

At least one control circuits of the appropriate stepper motor is shorted to voltage when motor starts moving. Faults are not detected when motor is already running or target position is already reached.

At least one control circuits of the appropriate stepper motor is shorted to ground or open when motor starts moving. Faults are not detected when motor is already running or target position is already reached.

• The affected output will be switched off for hardware protection.
• All stepper motors are deactivated.

• The affected output will be switched off for hardware protection.
• The affected stepper motor is deactivated.

The condition for setting the DTC is no longer present.

During diagnosis, it is important to verify that the air control door and any associated components (linkage, cams, gears, etc.) operate properly. Inspect for any conditions that may limit or prevent the air control door from moving smoothly or moving through its full range of travel. Any mechanical issues should be corrected first, before proceeding with electrical diagnosis.

HVAC Schematics

Master Electrical Component List

Automatic HVAC Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Perform theActuator Recalibration procedure.
2. Verify the concern or DTC has been corrected.
• If the concern or DTC has not been corrected
1. Verify DTC B023A is not set.
• If DTC B023A is set

  Refer to Circuit/System Testing — DTC B023A.

• If DTC B023A is not set

  Refer to Circuit/System Testing — DTC B0223, B0233, B0408 or B0418.

• If the concern or DTC has been corrected
3. All OK.

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the components listed below. It may take up to 2 min for all vehicle systems to power down.
• M37 Mode Door Actuator
• M46 Air Recirculation Door Actuator
• M6L Air Temperature Door Actuator — Left
• M6R Air Temperature Door Actuator — Right
2. Disconnect the X3 and X4 harness connectors at the K33 HVAC Control Module.
3. Test for infinite resistance between the K33 HVAC Control Module 12 V reference circuit terminal 15 X3 and ground.
• If less than infinite resistance

  Repair the short to ground on the circuit.

• If infinite resistance
4. Ignition ON.
5. Test for less than 1 V between the K33 HVAC Control Module 12 V reference circuit terminal 15 X3 and ground.
• If 1 V or greater

  Repair the short to voltage on the circuit.

• If less than 1 V
6. Connect the harness connectors at the K33 HVAC Control Module, ignition ON.
7. Clear all DTCs.
8. Verify DTC B023A is not set.
• If the DTC is set.

  Replace the K33 HVAC Control Module.

• If the DTC is not set.
9. Verify DTC B023A does not set after connecting each of the components listed below one at a time and operating them through their full range.
• M37 Mode Door Actuator
• M46 Air Recirculation Door Actuator
• M6L Air Temperature Door Actuator — Left
• M6R Air Temperature Door Actuator — Right
• If the DTC sets

  Replace the component that was connected immediately before the DTC set.

• If the DTC does not set
10. All OK.

1. Ignition OFF, disconnect the harness connector at the appropriate door actuator, ignition ON.

Note: If more than one actuator is affected, test the B+ circuit at each actuator.

2. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground.
• If the test lamp does not illuminate
1. Ignition OFF, remove the test lamp and disconnect the harness connector at the K33 HVAC Control Module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K33 HVAC control module.
• If the test lamp illuminates
3. Ignition ON, command the appropriate actuator with a scan tool.
4. Verify a test lamp is flashing on and off when connected between the B+ circuit terminal 2 and each control circuit terminal listed below:
• Control Circuit - terminal 1
• Control Circuit - terminal 3
• Control Circuit - terminal 4
• Control Circuit - terminal 6
• If the test lamp is always OFF
1. Vehicle OFF, disconnect the harness connector at the K33 HVAC control module. Vehicle in Service Mode.
2. Test for less than 1 V between the control circuit and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V
3. Vehicle OFF.
4. Test for less than 2 Ω in the control circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K33 HVAC Control Module.
• If the test lamp is always ON
1. Ignition OFF, remove the test lamp and disconnect the harness connector at the K33 HVAC Control Module, ignition ON.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K33 HVAC Control Module.
• If the test lamp is flashing On and Off
5. Test or replace the actuator.

Perform the Diagnostic Repair Verification after completing the repair.

• HVAC Component Replacement Reference
• Control Module References for control module replacement, programming and setup