Engine Coolant Temperature Sensor 1 - Voltage Out of Range
The engine coolant temperature sensor is reporting a voltage that is too high or too low.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The engine coolant temperature sensor measures the coolant temperature but is sending a signal that doesn't match expected levels, which can indicate a bad sensor or wiring issue.
What the computer is actually seeing
The ECM expects the coolant temperature to be between 140°F and 220°F (60°C to 104°C) and the signal voltage from the sensor to be roughly between 0.5V (cold) and 4.5V (hot). If the voltage is outside this range, the code triggers.
What a healthy reading looks like
Sensor voltage should range between 0.5V (approx. 140°F) to 4.5V (approx. 220°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.
- 11. Inspect the engine coolant level. Ensure it's at the recommended level. If low, top it off and retest.
- 22. Visually inspect the wiring and connectors for damage or corrosion. Repair as needed and retest.
- 33. Using a multimeter, check the voltage output of the coolant temperature sensor at the ECM connector. Expected range is 0.5V to 4.5V. If out of range, replace the sensor.
- 44. If sensor voltage is normal, check continuity and resistance in the wiring harness between the sensor and the ECM. If the harness is faulty, repair or replace it.
Common causes
- Faulty engine coolant temperature sensor
- Open or shorted wiring harness
- Corroded connectors
- Low coolant level
- Faulty engine control module (ECM)
Typical repair cost
$$ (200-$600)
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally drivable, but the engine performance may suffer or the vehicle may enter limp mode.
Will this code come back after clearing?
If the underlying issue isn't fixed, the code will likely return after driving a short distance.
Why does this code sometimes pair with other SPN codes?
Multiple codes can indicate related issues, like faulty sensors or wiring problems affecting engine performance.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →