Engine Coolant Temperature Sensor - Circuit Performance Problem
The engine coolant temperature sensor reading is outside expected parameters.
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What it means (plain English)
The sensor that measures how hot the engine coolant is acting up and sending odd readings to the engine computer.
What the computer is actually seeing
The engine control module (ECM) sees a coolant temperature value that is too high or too low compared to standard operating conditions, which might be due to sensor failure or circuit issues.
What a healthy reading looks like
Coolant temperature should be between 180°F to 220°F (82°C to 104°C) 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. It should be between the minimum and maximum marks. If low, top off and retest.
- 22. Inspect the wiring and connector to the coolant temperature sensor for damage or corrosion. Repair if necessary.
- 33. Use a scan tool to check the actual coolant temperature reading from the sensor. Compare it to the expected values above.
- 44. If the reading is unrealistic (like too high or too low), replace the coolant temperature sensor and retest.
- 55. If the reading appears correct, check for any associated fault codes and consult wiring diagrams for circuit integrity.
Common causes
- Faulty engine coolant temperature sensor
- Open or short in sensor wiring
- Corroded connector terminals
- Coolant leaks affecting temperature readings
- ECM software issues
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this fault code active?
It's moderate severity, so the vehicle is drivable but should be fixed soon to avoid potential overheating issues.
Will this code come back after clearing it?
It may come back if the underlying issue isn't fixed, like a bad sensor or wiring problem.
Why does this code sometimes pair with SPN 1973?
SPN 1974 (coolant temperature) and SPN 1973 (temperature too high) are related, as a failing sensor can incorrectly report high temperatures.
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