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 provide an overview of each diagnostic category.

DTC Descriptors

DTC B0460 00 : Coolant Heater Overheat Sensor Circuit Low

DTC B0462 00 : Coolant Heater Overheat Sensor Circuit Open

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Coolant Heater Overheat Sensor Supply Voltage Circuit

B0460 00

B0462 00

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--

Coolant Heater Overheat Sensor Ground Circuit

--

B0460 00

B0462 00

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Circuit/System Description

The fuel operated heater uses a coolant heater overheat sensor to protect the unit for over temperature conditions.

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.

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Cooling System Connector End Views

Electrical Information Reference

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

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Start the vehicle. Observe the coolant heater over heat sensor scan tool parameter . The scan tool parameter should display between 0.09-4.9 volts.

Component Testing

  1. Ignition OFF, disconnect the 14-pin coolant heater module connector from the module.
  2. Test the coolant heater over heat sensor resistance.
  3. Compare the readings with the Temperature vs Resistance table and verify that the resistance is within 5 percent of the specification.
  4. If the resistance vs temperature reading is not within 5 percent, replace the coolant heater overheat sensor.
  5. If the coolant heater overheat sensor 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