For 1990-2009 cars

### Diagnostic Instructions

• | 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

### DTC Descriptors

DTC B0228 29 : Recirculation Door Motor Circuit Too Few Pulses
DTC B0228 2A : Recirculation Door Motor Circuit Too Many Pulses
DTC B0228 61 : Recirculation Door Motor Circuit Stuck
DTC B0238 29 : Defogger Door Motor Circuit Too Few Pulses
DTC B0238 2A : Defogger Door Motor Circuit Too Many Pulses
DTC B0238 61 : Defogger Door Motor Circuit Stuck
DTC B0253 29 : Vent/Floor Door Motor Circuit Too Few Pulses
DTC B0253 2A : Vent/Floor Door Motor Circuit Too Many Pulses
DTC B0253 61 : Vent/Floor Door Motor Circuit Stuck
DTC B0408 29 : Drivers Air Mix Door Motor Circuit Too Few Pulses
DTC B0408 2A : Drivers Air Mix Door Motor Circuit Too Many Pulses
DTC B0408 61 : Drivers Air Mix Door Motor Circuit Stuck
DTC B0418 29 : Passengers Air Mix Door Motor Circuit Too Few Pulses
DTC B0418 2A : Passengers Air Mix Door Motor Circuit Too Many Pulses
DTC B0418 61 : Passengers Air Mix Door Motor Circuit Stuck

### Circuit/System Description

The actuators operate using 5 circuits. A 12-volt reference, low reference, signal circuit and two bi-directional 0 or 12 volt control circuits. The HVAC control module supplies a low reference and 12-volt reference to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. As the actuator door changes position the door position signal circuit voltage also changes. The two bi-directional control circuits enable the actuator to operate. Both circuits are set to 0 volts when the HVAC control module detects, from the feedback potentiometer, that the actuator is in the desired position. In order to move the actuator, the HVAC control module switches the appropriate control circuit to 12 volts.

### Conditions for Running the DTC

• | The ignition is ON.

• | Ignition voltage is between 9-16 volts.

• | The HVAC module is ON.

### Conditions for Setting the DTC

#### Sub Code: 29

• | The HVAC control module detects the door position signal circuit is supplying too few pulses.

• | Door position signal circuit has an open/high resistance.

• | Actuator door control lever is jammed.

#### Sub Code: 2A

• | The HVAC control module detects the door position signal circuit is supplying too many pulses.

• | Actuator door control lever is disconnected.

#### Sub Code: 61

• | The HVAC control module fails to detect any signal from the door position signal circuit.

• | Door position signal circuit has an open/high resistance.

• | Actuator position sensor failure.

• | Actuator door control lever is jammed.

### Action Taken When the DTC Sets

• | The actuator driver circuits are deactivated.

• | The HVAC control module will set the appropriate code.

### Conditions for Clearing the DTC

• | The condition for setting the DTC is no longer present.

• | The history DTC will clear after 50 fault-free ignition cycles.

• | The DTC can be cleared with a scan tool.

### Reference Information

#### Schematic Reference

HVAC Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

• | Access the appropriate actuator door and visually inspect movement when requested from the HVAC control module.

• | Using a scan tool, select actuator testing and visually inspect actuator door movement.

• | Visually inspect actuator door pivots for evidence of breakage or damage.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 3 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 10-12.5 volts between the 12-volt reference circuit terminal 5 and ground.

⇒ | If less than the specified range, test the 12-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 12-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.

4. Verify the scan tool Door Position parameter is greater than 95 percent.

⇒ | If less than the specified range, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the HVAC control module.

5. Install a 3A fused jumper wire between the signal circuit terminal 4 and the low reference circuit terminal 3. Verify the scan tool Door Position parameter is less than 3 percent.

⇒ | If greater 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 OFF, test for less than 10 ohms between the control circuit terminal 1 and ground.

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

7. Ignition OFF, test for less than 10 ohms between the control circuit terminal 2 and ground.

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

8. Connect a test lamp between control circuit terminal 1 and control circuit terminal 2.
9. Ignition ON, command the appropriate actuator door in both directions with a scan tool. The test lamp should turn ON and OFF when commanded in both directions.

⇒ | If the test lamp remains OFF during either of the commands, test for a short to ground on either control circuit. If the circuits test normal, replace the HVAC control module.

10. If both circuits test normal, test or replace the actuator.

### Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | HVAC Control Module Programming and Setup

• | Recirculation Actuator Replacement

• | Temperature Valve Actuator Replacement - Left Side

• | Temperature Valve Actuator Replacement - Right Side

• | Defroster Valve Actuator Replacement

• | Floor Air Valve Actuator Replacement

• | Auxiliary Mode Valve Actuator Replacement