B0478

DTC B0465, B0467, or B0478

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 provide an overview of each diagnostic category.

DTC Descriptors

DTC B0465 00
- Auxiliary Heater Flame Sensor Circuit Low

DTC B0467 00
- Auxiliary Heater Flame Sensor Circuit Open

DTC B0478 00
- Flame Off for Minimum Power

Diagnostic Fault Information






Circuit/System Description

The fuel operated coolant heater uses a coolant heater combustion sensor to monitor flame temperature.

Conditions for Running the DTC

Engine is running.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

Fuel operated coolant heater is disabled.

Conditions for Clearing the DTC

DTC must be cleared with a scan tool.

Circuit/System Verification

Start the vehicle. Observe the Flame Temperature Sensor scan tool parameter. The scan tool parameter should display between 0.09-4.9 volts.

Component Testing

1. Ignition OFF, disconnect the harness connector at the flame temperature sensor.
2. Ignition OFF, test for less than1 ohm between the low reference circuit and ground.

^ If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the coolant heater.

3. Ignition ON, verify the scan tool Flame Temperature Sensor parameter is greater than 4.5 volts.

^ If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the coolant heater.

4. Install a 3A fused jumper wire between the signal circuit and the low reference circuit. Verify the scan tool Flame Temperature Sensor parameter is less than .5 volts.

^ If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the coolant heater.

5. If all circuits test normal, test or replace the flame temperature sensor.

Repair Instructions

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

* Heater Coolant Heater Combustion Sensor Replacement
* Heater Coolant Heater Replacement