Engine Coolant Temperature Sensor Circuit High
Coolant temperature sensor signal is too high.
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What it means (plain English)
The engine control unit (ECU) thinks the engine coolant is way hotter than it actually is because the sensor is malfunctioning.
What the computer is actually seeing
The ECU is reading a coolant temperature above 250°F (121°C), which is not possible under normal operating conditions.
What a healthy reading looks like
Normal coolant temperature readings should be between 180°F to 220°F (82°C to 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.
- 1Check the engine coolant level and ensure it's within the operating range; refill if low.
- 2Inspect the coolant temperature sensor wiring for damage, corrosion, or loose connections; repair as needed.
- 3Use a scan tool to read the current coolant temperature; if it's above 250°F (121°C), proceed to the next step.
- 4Disconnect the coolant temperature sensor and check for proper resistance; it should measure between 2000-3000 ohms at 77°F (25°C). If outside this range, replace the sensor.
- 5Re-check the wiring to the ECU for shorts or open circuits; ensure continuity and good connections.
- 6If all else checks out, consider reprogramming or replacing the ECU if fault persists.
Common causes
- Faulty coolant temperature sensor
- Wiring issues (shorts or corrosion) in the sensor circuit
- Bad engine grounds affecting sensor readings
- ECU software issues
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; you may experience overheating, so fix it soon.
Will this code come back after resetting?
If the issue is fixed, it shouldn't; if it reappears, further diagnostics are needed.
Why does this code pair with SPN 422?
SPN 422 is usually a result of high coolant temperature detection; they often trigger together.
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