Engine Coolant Temperature Sensor Circuit High
The engine coolant temperature sensor is sending a high voltage signal.
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What it means (plain English)
The engine computer thinks the coolant is hotter than it really is because the sensor is sending too high of a voltage signal, which can lead to poor engine performance and overheating.
What the computer is actually seeing
The engine control module (ECM) expects a voltage signal from the coolant temperature sensor typically between 0.5V (cold) to 4.5V (hot). A reading above this range indicates a fault.
What a healthy reading looks like
Normal coolant temperature should show a resistance of about 2,500 to 3,500 ohms at 70°F (21°C). Voltage should be between 0.5V and 4.5V.
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. Inspect the wiring and connector for the coolant temperature sensor. Look for any damage, corrosion, or loose connections. If found, repair as necessary.
- 22. Use a multimeter to check the voltage at the coolant temperature sensor connector. At engine operating temperature the voltage should be between 0.5V and 4.5V. If voltage is significantly above 4.5V, proceed to the next step.
- 33. Disconnect the coolant temperature sensor and measure resistance across the sensor terminals with the engine cold. It should be between 2,500 to 3,500 ohms at around 70°F. If it is out of spec, replace the sensor.
- 44. If the sensor tests good, check for short circuits in the wiring from the sensor to the ECM. Repair any shorts found.
- 55. If all tests are within specifications, consider potential issues with the engine (coolant leaks, overheating) that could affect sensor readings.
Common causes
- Wiring issues (frayed or damaged wires) to the sensor
- Faulty coolant temperature sensor
- Poor electrical connection (corrosion or loose connectors)
- Engine overheating due to unrelated issues
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It’s moderate severity; you can drive it but fix it soon to avoid overheating issues.
Will this code clear on its own?
Possible, but if the problem persists, it will likely return.
Why does this code sometimes pair with SPN 1684?
SPN 1684 indicates that the ECM has detected an unusual temperature reading, often related to issues with the coolant temperature sensor itself.
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