Engine Coolant Temperature Too High
The engine's coolant temperature is too high, indicating potential overheating.
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What it means (plain English)
The engine computer is seeing that the coolant temperature is above 250 degrees Fahrenheit for more than 5 seconds, which is too hot. This can cause engine damage if not addressed quickly.
What the computer is actually seeing
The ECM continuously monitors the coolant temperature sensor's voltage signal, which typically ranges from 0.5 volts (cold) to 4.5 volts (hot). A reading over 250°F triggers this code.
What a healthy reading looks like
Expected coolant temperature should be between 160°F and 220°F during normal operation.
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 the coolant level in the reservoir; top off if low. Is the level adequate? - If NO, refill coolant and check for leaks; if YES, proceed to step 2.
- 22. Inspect the coolant temperature sensor wiring and connector for damage. Is the wiring intact and the connector clean? - If NO, repair the wiring/connector; if YES, proceed to step 3.
- 33. Use a scan tool to check the live data of the coolant temperature reading. Is it consistent with the actual temperature? - If NO, replace the coolant temperature sensor; if YES, proceed to step 4.
- 44. Check the operation of the thermostat by observing the temperature change as the engine warms up. Does the temperature stabilize below 250°F? - If NO, replace the thermostat; if YES, check the radiator and coolant flow.
Common causes
- Low coolant level
- Faulty coolant temperature sensor
- Thermostat stuck closed
- Coolant leaks in the system
- Radiator blockage or failure
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
No, it is not safe to drive when the coolant temperature is too high, as it can lead to engine damage.
What happens if I ignore this warning?
Ignoring this can cause severe engine overheating and potentially lead to a complete engine failure.
Will this code come back after repair?
If the root cause is properly fixed, the code should not return unless there is an unrelated issue.
Working a real vehicle right now?
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