Engine Coolant Temperature Sensor 1 - Voltage Above Normal
The engine coolant temperature sensor is reporting a voltage that's too high for normal operation.
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What it means (plain English)
The engine coolant temperature sensor sends an electrical signal that tells the engine computer how hot the engine coolant is. If the voltage from this sensor is higher than what the computer expects (typically around 0.5-4.5V), it thinks there's too much coolant temperature, even if the engine is fine.
What the computer is actually seeing
The engine control module (ECM) expects the engine coolant temperature based on its operating range, usually between 180°F to 220°F (82°C to 104°C). When the voltage exceeds the typical range (over 4.5V), it triggers the fault code.
What a healthy reading looks like
Coolant temperature should usually produce between 0.5V (below freezing) to 4.5V (above 220°F or 104°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.
- 1Check the wiring and connectors to the coolant temperature sensor for damage or corrosion. Repair if needed.
- 2Measure the voltage at the engine coolant temperature sensor connector. A normal reading is between 0.5V to 4.5V. If it's over 4.5V, go to the next step.
- 3Disconnect the sensor and check the resistance across the terminals. It should drop with increasing temperature (roughly 200 ohms at 180°F). If it's shorted or outside specs, replace it.
- 4If after replacing the sensor the issue persists, check the wiring harness from the sensor to the ECM for shorts to power or ground.
Common causes
- Shorted wiring to the sensor
- Failed engine coolant temperature sensor
- Faulty engine control module (rare)
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally drivable, but overheating could occur if coolant temperature is truly high, so keep an eye on the temperature gauge.
Will the code come back after resetting?
Yes, if the underlying issue isn't fixed, the code will likely return.
Why does this code pair with SPN 1918?
SPN 1918 deals with the coolant sensor signal being out of range, while SPN 1919 indicates high voltage specifically.
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