Cooling System Temperature Sensor 1 High
The cooling system temperature sensor is reporting a high temperature reading.
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What it means (plain English)
The cooling temperature sensor measures the temperature of the engine coolant. If it reports a value that's too high, it means the computer thinks the engine is excessively hot.
What the computer is actually seeing
The Engine Control Module (ECM) is receiving a signal from the cooling system temperature sensor that is outside its normal operating range, typically over 230°F (110°C).
What a healthy reading looks like
Normal coolant temperature should be between 180°F and 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.
- 11. Visually inspect the wiring and connectors for the coolant temperature sensor. Look for fraying, corrosion, or loose connections. Repair or replace as needed.
- 22. Check the coolant level in the reservoir and radiator. The level should be within the manufacturer's specified range. Add coolant if low and retest.
- 33. Use a scan tool to read the current temperature from the cooling temperature sensor. Compare this value to the engine temperature gauge reading. Confirm that the sensor and gauge are giving similar readings.
- 44. If the readings are inconsistent, remove the sensor and test it using a multimeter. It should show resistance changes corresponding to the coolant temperature. A normal sensor usually shows around 2-3k ohms at 70°F (21°C).
- 55. If the sensor is faulty, replace it. If the sensor is working but the code persists, inspect the wiring further back to the ECM. Test for continuity and shorts. Repair as necessary.
Common causes
- Faulty cooling temperature sensor
- Wiring issues (short circuit or open circuit)
- Coolant leaks leading to low coolant levels
- Engine overheating due to cooling system failures
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Moderate severity means you should fix it soon, but it may still be drivable. Watch for overheating.
Will this code come back after clearing it?
If the underlying issue is not resolved (like a faulty sensor or wiring), the code will likely come back after clearing.
Why does this code pair with SPN 119?
SPN 119 is a related code indicating a cooling temperature sensor issue, suggesting similar faults within the cooling system sensor circuit.
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