Engine Over Temperature

The engine’s coolant temperature sensor (CTS) is telling the computer that the engine is running hotter than normal, usually above 240°F (116°C). This can cause engine parts to warp and fail if not addressed quickly.

The Engine Control Module (ECM) constantly monitors the coolant temperature via the CTS, which outputs a voltage ranging from 0.5V (cold) to 4.5V (hot). It expects values around 1.0V to 2.5V during normal operation when temperatures are between 180°F (82°C) and 220°F (104°C).

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 coolant level in the reservoir and radiator. Add coolant if low. Decision: If coolant was low, refill and monitor for leaks.
2. 22. Inspect wiring and connector at the coolant temperature sensor for damage or corrosion. Decision: If wiring is damaged, repair it.
3. 33. Measure the coolant temperature at the sensor using a scan tool and compare it to a known-good temperature reading. Decision: If the reading significantly diverges from expected values, replace the coolant temperature sensor.
4. 44. Check for any obstructions in the radiator or air intake that may affect cooling. Decision: If obstruction is found, clear it and monitor temperature again.
5. 55. Test the thermostat operation by checking if the engine reaches normal operating temperature within a reasonable timeframe (10-15 minutes). Decision: If it doesn't, replace the thermostat.

• Low coolant level
• Faulty coolant temperature sensor
• Coolant leaks
• Clogged radiator
• Failed thermostat
• Water pump failure

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