B0447

DTC B0445, B0446, or B0447

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.
* 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 heater uses an auxiliary heater fuel pump to supply fuel to the combustion chamber through the glow plug socket over the glow plug to ignite the air fuel mixture. Once a stable flame has formed, the glow plug will turn OFF.

Conditions for Running the DTC

Engine is running.

Conditions for Setting the DTC

Fuel operated heater has recognized out of range condition formore 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.

Circuit/System Verification

Start the vehicle. Observe the Coolant Heater Fuel Pump and desired fuel pump scan tool parameters. The scan tool parameters should match. Above 85°C (185°F), the coolant heater will no longer pump fuel. Above 80-85°C (176-185°F), the coolant pump will operate at a reduced level. Above 20-75°C (68-176°F), the coolant pump will operate at full capacity.

Component Testing

1. Ignition OFF, disconnect the 10 pin coolant heater module pigtail connector from the module.
2. Test the coolant heater fuel pump resistance.
3. Compare the readings with the Temperature vs Resistance table and verify that the resistance is within 5 percent of the specification.

• If the resistance vs temperature reading is not within 5 percent, replace the coolant heater fuel pump.

4. If the coolant heater fuel pump tests normal, replace the coolant heater.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

* Heater Coolant Heater Glow Plug Replacement
* Heater Coolant Heater Replacement Verification Tests