Engine Coolant Temperature - Abnormal Temperature
Indicates that the engine coolant temperature is higher than expected.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer is sensing that the coolant temperature is too high, which can mean the engine is overheating or there's a cooling problem.
What the computer is actually seeing
The computer reads the coolant temperature sensor signal, typically between 0 to 5 volts depending on the temperature. A value higher than 240°F (115°C) can trigger this code.
What a healthy reading looks like
Coolant temperature should be between 180°F (82°C) and 220°F (104°C) when the engine is at operating temperature.
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. Is it low? If yes, refill and retest the vehicle. Decision: If the level is normal, continue to step 2. If low, address the leak.
- 22. Inspect for leaks around the radiator, hoses, and engine. Are there any visible leaks? If yes, repair leaks and retest. Decision: If no leaks, continue to step 3.
- 33. Test the thermostat. Is it stuck closed? If yes, replace the thermostat and retest. Decision: If functioning correctly, continue to step 4.
- 44. Check the coolant temperature sensor signal with a scan tool. Is it fluctuating between 0-5 volts as temperature changes? If not, replace the sensor and retest. Decision: If the signal is good, continue to step 5.
- 55. Inspect the wiring and connectors to the coolant temperature sensor. Are they in good condition? If damaged, repair or replace them and retest.
Common causes
- Low coolant level
- Failed thermostat
- Coolant leaks
- Bad coolant temperature sensor
- Air trapped in cooling system
Typical repair cost
$$$
Related codes
Frequently asked questions
Can I still drive with this code?
It's not recommended as the engine may overheat, leading to severe damage.
Will this code come back after repairs?
If all issues are fixed correctly, the code should not return.
Why is this code showing along with SPN 42?
SPN 42 indicates coolant level issues, often linked to overheating or sensor faults.
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