B0418

DTC B0223, B0233, B0248, B0268, B0408, B0418, or B0428

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.

DTC Descriptors
DTC B0223 04
- Recirculate Position Command Circuit Open

DTC B0223 05
- Recirculate Position Command Circuit Short to Battery or Open

DTC B0223 06
- Recirculate Position Command Circuit Short to Ground or Open

DTC B0223 61
- Recirculation Actuator Stuck

DTC B0233 04
- Air Flow Control Circuit Open

DTC B0233 05
- Air Flow Control Circuit Short to Battery or Open

DTC B0233 06
- Air Flow Control Circuit Short to Ground or Open

DTC B0233 61
- Air Flow Control Actuator Stuck

DTC B0408 04
- Temperature Control 1 Circuit Open

DTC B0408 05
- Temperature Control 1 Circuit Short to Battery or Open

DTC B0408 06
- Temperature Control 1 Circuit Short to Ground or Open

DTC B0408 61
- Temperature Control 1 Circuit Actuator Stuck

DTC B0418 04
- Temperature Control 2 Circuit Open

DTC B0418 05
- Temperature Control 2 Circuit Short to Battery or Open

DTC B0418 06
- Temperature Control 2 Circuit Short to Ground or Open

DTC B0418 61
- Temperature Control 2 Circuit Actuator Stuck

Diagnostic Fault Information





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 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.

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

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 shorted to ground shorted to voltage or open.

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

* The DTC becomes history when the HVAC control module no longer detects the condition that set the DTC.
* 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 (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

* Air Delivery Description and Operation (Air Delivery Description and Operation)
* Air Temperature Description and Operation (Air Temperature Description and Operation)

Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

Scan Tool Reference

Control Module References (Programming and Relearning) 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 or terminal C for the mode actuator. 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.

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Recirculation Actuator Replacement (Recirculation Actuator Replacement)
* Mode Actuator Replacement (Impala) (Mode Actuator Replacement (Impala))
* Temperature Valve Actuator Replacement - Left Side (Temperature Valve Actuator Replacement - Left Side)
* Temperature Valve Actuator Replacement - Right Side (Temperature Valve Actuator Replacement - Right Side)
* Control Module References (Programming and Relearning) for HVAC control module setup, replacement, and programming