B0446

DTC B0445, B0446, or B0447

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 B0445 00

-
Auxiliary Heater Fuel Pump Circuit Low

DTC B0446 00

-
Auxiliary Heater Fuel Pump Circuit High

DTC B0447 00

-
Auxiliary Heater Fuel Pump Circuit Open

Diagnostic Fault Information






Circuit/System Description

The fuel operated coolant heater uses a fuel pump to supply fuel to the combustion chamber.

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 DiagramsHVAC Schematics Electrical Diagrams

Connector End View Reference

Component Connector End Views 1-2 Shift Solenoid (SS) Valve (M30)

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 Control Module References for scan tool information

Circuit/System Verification

Ignition ON, command the Auxiliary Heater Fuel Pump ON and OFF with the scan tool. Verify the fuel pump turns ON and OFF as commanded.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the fuel pump.

2. Ignition OFF, test for less than 5 ohms between the ground circuit terminal 1 and ground.

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

3. Install a test lamp between the control circuit terminal 2 and ground circuit terminal 1.

4. Ignition ON, command the fuel pump 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 fuel pump.

Repair Instructions

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

* Heater Coolant Heater Fuel Pump Replacement Service and Repair

* Heater Coolant Heater Replacement Heater Coolant Heater Replacement