Engine Coolant Temperature Sensor - Voltage Above Normal
The engine coolant temperature sensor is reporting a voltage that's higher than expected.
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What it means (plain English)
The engine control module (ECM) uses the coolant temperature sensor to monitor the engine's temperature. If the ECM sees a voltage reading above a certain threshold, it thinks the engine is overheating or the sensor is faulty.
What the computer is actually seeing
The ECM expects the coolant temperature sensor to output a voltage in a specific range (typically 0.5V to 4.5V). When it sees a voltage above 4.5V, it triggers this fault code.
What a healthy reading looks like
Coolant temperature sensor output should be between 0.5V and 4.5V; if it exceeds 4.5V, it's considered out of spec.
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 wiring and connector at the coolant temperature sensor. Look for frayed wires or corrosion. If any issues found, repair them and retest.
- 22. Measure the voltage at the coolant temperature sensor with the engine at operating temperature. If it's above 4.5V, proceed to step 3. If it's within range, consider the sensor faulty and replace it.
- 33. Disconnect the sensor and check the wiring harness for shorts to voltage. If no shorts are present, replace the coolant temperature sensor and clear the code.
Common causes
- Faulty coolant temperature sensor
- Wiring issues or short circuits in the sensor circuit
- ECM software glitch or fault
- Coolant leaks leading to false readings
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
While you can drive the vehicle, it's not recommended as it may affect engine performance and could cause overheating.
Will this code come back after repair?
If the underlying issue is fixed correctly, it should not reappear.
Why does this code sometimes pair with SPN 100?
SPN 100 also relates to engine temperature readings, so issues with the sensor or wiring can trigger both codes.
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