B0452

DTC B0449, B0450, B0451, or B0452

Diagnostic Instructions

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

DTC Descriptors
DTC B0449 00
- Auxiliary Heater Blower Fan Circuit Range/Performance

DTC B0450 00
- Auxiliary Heater Blower Fan Circuit Low

DTC B0451 00
- Auxiliary Heater Blower Fan Circuit High

DTC B0452 00
- Auxiliary Heater Blower Fan Circuit Open

Diagnostic Fault Information





Circuit/System Description

The fuel operated heater uses a coolant heater blower motor to supply oxygen onto the combustion chamber so the air fuel mixture will ignite when the glow plug is activated.

Conditions for Running the DTC

Engine is running.

Conditions for Setting the DTC

The fuel operated heater has recognized out of range condition for more than 2.5 seconds.

Action Taken When the DTC Sets

The fuel operated coolant heater is disabled.

Conditions for Clearing the DTC

* A current DTC will clear when the conditions for setting the DTC are no longer present.
* A history DTC will clear after 40 malfunction-free ignition cycles.

Reference Information
Schematic Reference

HVAC Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Description and Operation

Air Temperature Description and Operation (Air Temperature)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, command the Blower Motor ON and OFF with the scan tool. Verify the blower motor turns ON and OFF as commanded.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the blower motor.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal and ground.

• If greater than the specified range, replace the coolant heater.

3. Install a test lamp between the control circuit terminal and low reference circuit terminal.
4. Ignition ON, command the blower motor ON and OFF using a scan tool. Verify the test lamp turns ON and OFF with each command.

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the coolant heater.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the coolant heater.

5. If all circuits test normal, test or replace the blower motor.

Repair Instructions

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

* Heater Coolant Heater Blower Replacement (Heater Coolant Heater Blower Replacement)
* Heater Coolant Heater Replacement (Heater Coolant Heater Replacement)