Engine Coolant Temperature Sensor - High

The coolant temperature sensor is telling the engine computer that the engine is running way too hot, usually over 240°F (115°C).

The engine control module (ECM) monitors the coolant temperature sensor and expects readings up to 240°F (115°C). If it sees a voltage signal indicating a temperature above that, it triggers the SPN 2080 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. 11. Check engine coolant level: Ensure the coolant is at the correct level in the reservoir. If low, fill and retest. Decision: If coolant was low, monitor for leaks to confirm it was the issue.
2. 22. Inspect the wiring and connectors of the coolant temperature sensor: Look for frayed wires, corrosion, or poor connections. Decision: If damaged, repair or replace as needed and retest.
3. 33. Use a scan tool to monitor the coolant temperature sensor reading while the engine is running: Confirm if it stays above 240°F (115°C). Decision: If it stays high with no visible overheating, suspect the sensor itself for failure.
4. 44. Measure the resistance of the coolant temperature sensor: At room temperature, it should be around 2.5k ohms. Decision: If out of spec, replace the sensor and retest.
5. 55. Check the engine for signs of overheating: Inspect for blown head gaskets or cracks if the issue continues, which could be causing actual overheating.

• Faulty coolant temperature sensor
• Wiring issues (shorts or opens) in the sensor circuit
• Coolant leaks causing insufficient coolant levels
• Thermostat stuck closed
• Overheating engine due to other issues

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