Engine Over Temperature
The engine temperature is higher than the normal operating range.
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What it means (plain English)
The engine's coolant temperature has exceeded normal limits, usually above 220°F (104°C), indicating potential overheating issues.
What the computer is actually seeing
The engine control unit (ECU) monitors the coolant temperature sensor signal, expecting it to stay within the normal range (typically 180°F to 220°F). When the signal indicates a temperature above 220°F, it triggers SPN 804.
What a healthy reading looks like
Coolant temperature should typically be between 180°F (82°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 the engine coolant level; must be at the correct level (usually at the 'full' mark). If low, refill and check for leaks.
- 22. Inspect the coolant temperature sensor connector for damage or corrosion. Repair or replace as needed.
- 33. Start the engine and monitor the coolant temperature using a scan tool or gauge; check for expected values between 180°F and 220°F.
- 44. If overheating persists, check for coolant leaks in hoses and engine; repair any found leaks.
- 55. Test the thermostat operation by checking the engine temperature as it warms up; the thermostat should open at the designated temperature (usually around 190°F).
Common causes
- Low coolant level
- Cooling system leak
- Failed thermostat
- Faulty coolant temperature sensor
- Cooling fan not operating
Typical repair cost
$$$
Related codes
Frequently asked questions
Can I drive the vehicle with this code?
No, it's not safe to drive; engine overheating can cause severe damage.
Will this code come back after clearing it?
Yes, if the underlying issue isn't fixed, the code will return.
What should I do if the temperature gauge is normal but the code persists?
Check the coolant temperature sensor for faults, as it might be giving false readings.
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