Engine Coolant Temperature Sensor 1 - Voltage Above Normal
The engine coolant temperature sensor is reporting a voltage that's too high.
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What it means (plain English)
The engine coolant temperature sensor sends a voltage signal to the computer based on coolant temperature. Normally, it should be between 0.5 to 4.5 volts. If it exceeds this range, the computer sees a fault and triggers this code.
What the computer is actually seeing
The engine control module (ECM) sees a signal voltage from the coolant temperature sensor that is higher than the expected maximum, often greater than 4.5 volts, indicating a potential sensor failure or wiring issue.
What a healthy reading looks like
Coolant temperature sensor should output between 0.5 to 4.5 volts, corresponding to a temperature range of approximately -40°F to 240°F (-40°C to 115°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. Inspect the wiring and connector at the engine coolant temperature sensor for damage or corrosion. Repair as necessary.
- 22. Check the resistance of the coolant temperature sensor using a multimeter. Expect resistance varies with temperature; at 212°F (100°C) it should be around 220-240 ohms. If outside this range, replace the sensor.
- 33. Check the voltage at the sensor connector with the ignition on and the engine off. Should be between 0.5 to 4.5 volts. If voltage is excessively high with a good sensor, check for shorted wires.
- 44. If all connections are good, and the sensor tests normal, consider replacing the ECM if it’s sending incorrect signals.
Common causes
- Faulty engine coolant temperature sensor
- Short circuit in the wiring harness
- Corrosion or poor connections at the sensor
- Faulty engine control module (ECM)
Typical repair cost
$$ - $$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It may be drivable, but excessive coolant temperature can lead to engine overheating. It's best to address it soon.
Will this fault come back after clearing?
If the cause isn't fixed, yes. Monitor the system after repair.
Why do I see this code when the engine isn't overheating?
The sensor could be faulty, sending incorrect voltage, or there may be wiring issues.
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