B0449

DTC B0449, B0450, B0451, or B0452

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

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

Action Taken When the DTC Sets
Fuel operated heater is disabled.

Conditions for Clearing the DTC
DTC must be cleared with a scan tool.

Reference Information

Schematic Reference
HVAC Schematics Electrical Diagrams

Connector End View Reference
Cooling System Connector End Views Connector Views

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
• Scan Tool Data ListScan Tool Testing and Procedures
• Scan Tool Data Definitions Scan Tool Testing and Procedures

Circuit/System Verification
Start the vehicle. Observe the Coolant Heater Blower Motor scan tool parameters. The scan tool parameters should display On when the heater is activated.

Component 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 lamps turns ON and OFF with each command.
- If the test lamps is always ON, test the control circuit for a short to voltage. If the circuits tests normal, replace the coolant heater.
- If the test lamps is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuits tests normal, replace the coolant heater.

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

Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
• Heater Coolant Heater Glow Plug Replacement Heater Coolant Heater Glow Plug Replacement
• Heater Coolant Heater Replacement Heater Coolant Heater Replacement