B0446

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


Circuit/System Verification

Start the vehicle, observe the Fuel Pump PWM 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. Between 80-85°C (176-185°F), the coolant pump will operate at a reduced level. Between 20-75°C (68-176°F), the coolant pump will operate at full capacity.

Circuit/System Testing

1. Ignition OFF, disconnect the coolant heater fuel pump connector at the coolant heater fuel pump.
2. Test for less than 10 ohms between the ground circuit terminal B and ground.

^ If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal A and the ground circuit terminal B.
4. Command the coolant heater fuel pump ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states

^ 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 coolant heater fuel pump.

Repair Instructions

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

* Heater Coolant Heater Fuel Pump Replacement
* Heater Coolant Heater Replacement