Engine Coolant Temperature - High
Engine coolant temperature exceeds normal operating range.
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What it means (plain English)
The engine computer is detecting that the coolant temperature is too high, which could lead to engine overheating.
What the computer is actually seeing
The engine control module (ECM) monitors the coolant temperature through a sensor. When the temperature goes beyond the set threshold (typically around 250°F or 121°C), the code triggers.
What a healthy reading looks like
Normal coolant temperature should be between 160°F (71°C) and 220°F (104°C).
Guided diagnostic — the DiagCoach way
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.
- 11. Check coolant level in the reservoir. Is it low? -> Top off and recheck if code returns.
- 22. Inspect wiring and connectors to the coolant temperature sensor. Are they intact and clean? -> Repair any damage and recheck.
- 33. Use a scanner to read the actual coolant temperature. Is it significantly higher than expected values? -> Replace the sensor if readings are abnormal.
- 44. Check the thermostat operation. Is it stuck closed? -> Replace thermostat if necessary and monitor if code comes back.
- 55. Inspect the radiator and hoses for blockages or leaks. Are they clear and in good shape? -> Flush the cooling system if needed.
Common causes
- Coolant leak
- Faulty temperature sensor
- Bad thermostat
- Restricted cooling system (clogged radiator)
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
No, driving with an overheating engine can cause severe damage.
What happens if I ignore this code?
Ignoring it can lead to engine failure due to overheating.
Why might this code appear after a recent coolant change?
If air is trapped in the system or the wrong coolant was used, it can lead to malfunction.
Working a real vehicle right now?
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