Engine Coolant Temperature Sensor Fault

The engine coolant temperature sensor measures the temperature of the coolant. If it's giving incorrect readings, the computer might think the engine is overheating or not warming up appropriately.

The engine control module (ECM) expects the coolant temperature to be within a certain range, typically 180°F to 220°F (82°C to 104°C) during normal operation. If the sensor reports a temperature outside of the expected range, it triggers this fault code.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 1Check the coolant level; ensure it's adequate and not leaking. Decision: if low, top off and retest.
2. 2Inspect the wiring and connectors at the coolant temperature sensor for damage or corrosion. Decision: if damaged, repair or replace.
3. 3Test the resistance of the coolant temperature sensor at ambient temperature using an ohmmeter; it should typically be around 10k ohms at 68°F (20°C). Decision: if resistance is out of spec, replace the sensor.
4. 4Start the engine and monitor the coolant temperature with a scan tool. It should rise steadily with engine temperature. Decision: if the readings are erratic or outside expected values, replace the sensor.

• Faulty engine coolant temperature sensor
• Wiring issues (shorts or opens) in the sensor circuit
• Poor connections at the sensor or ECM
• Coolant contamination affecting sensor performance

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