GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

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

DTC Descriptors

DTC B0455 00: Auxiliary Heater Coolant Sensor Circuit Low

DTC B0457 00: Auxiliary Heater Coolant Sensor Circuit Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Auxiliary Heater Coolant Sensor Signal

B0455 00

B0457 00

B0457 00

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Auxiliary Heater Coolant Sensor Low Reference

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B0457 00

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Circuit/System Description

The fuel operated heater uses an auxiliary heater coolant sensor to measure the coolant temperature.

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

Connector End View Reference

Component Connector End Views

Description and Operation

Air Temperature Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Engine running, observe the scan tool Coolant Temp. Sensor parameter. The parameter should be between 0.09-4.9 volts.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the coolant heater temperature sensor.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit and ground.
  3. 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.
  4. Ignition ON, verify the scan tool Coolant Temp. Sensor parameter is greater than 4.5 volts.
  5. If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the coolant heater.
  6. Install a 3A fused jumper wire between the signal circuit and the low reference circuit . Verify the scan tool Coolant Temp. Sensor parameter is less than 0.5 volts.
  7. 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.
  8. If all circuits test normal, test or replace the coolant temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Heater Coolant Heater Air Temperature Sensor Replacement
    •  Heater Coolant Heater Replacement