Engine Coolant Temperature Sensor 1 Voltage
Indicates a fault with the engine coolant temperature sensor voltage.
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What it means (plain English)
The engine computer is reading a voltage signal from the coolant temperature sensor that is outside of the expected range, which is usually between 0.5V to 4.5V depending on the temperature.
What the computer is actually seeing
The engine control unit (ECU) interprets the voltage signal from the coolant sensor to determine the engine temperature. If the voltage is too low (<0.5V) or too high (>4.5V), it triggers this fault code.
What a healthy reading looks like
Coolant temperature sensor should read between 0.5V (approx. -40°C / -40°F) and 4.5V (approx. 125°C / 257°F).
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.
- 1Check the wiring and connectors of the coolant temperature sensor for damage or corrosion.
- 2Verify coolant level; low coolant can affect temperature readings.
- 3Backprobe the coolant temperature sensor with a multimeter. Voltage should be between 0.5V and 4.5V. If out of range, replace the sensor if wiring is good.
- 4If the sensor voltage is correct, check the ECU for potential faults or internal errors.
Common causes
- Wiring issues such as shorts or open circuits in the sensor circuit.
- Defective coolant temperature sensor.
- Corroded or loose electrical connectors.
- Coolant leaks affecting sensor readings.
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderately severe; you're safe to drive but should address it soon to avoid engine performance issues.
Will this problem come back after fixing?
If the underlying issue with wiring or the sensor is resolved properly, it shouldn't come back.
Why does this code sometimes pair with SPN 2102?
Because SPN 2102 is related to a different temperature sensor, both could be affected by similar wiring issues or coolant system faults.
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