Engine Coolant Temperature Sensor 1 (Input Signal)
Engine coolant temperature sensor 1 is sending incorrect signals to the ECM.
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 how hot the engine coolant is. If it's reading incorrectly, it can cause engine performance issues or even overheating.
What the computer is actually seeing
The ECM expects the coolant temperature to be between 190°F to 220°F (88°C to 104°C) during normal operation. If the readings are below 160°F (71°C) or above 240°F (116°C), it triggers the fault code.
What a healthy reading looks like
Normal operation between 190°F (88°C) and 220°F (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 coolant level in the reservoir and radiator. Top off if low, then clear code and retest. If the code returns, proceed to next step.
- 2Inspect wiring and connectors on the coolant temperature sensor for damage or corrosion. Repair as necessary, clear code, and retest.
- 3Using a multimeter, check the resistance of the coolant temperature sensor at varying temperatures. Compare readings to manufacturer specifications. If outside limits, replace the sensor.
- 4Check for any coolant leaks that could affect sensor readings or engine temperature. Fix any leaks found and test the system.
Common causes
- Wiring issues at the coolant temperature sensor
- Faulty coolant temperature sensor
- Corrosion or damage to the connector
- Low coolant level
- ECM software glitch
Typical repair cost
$100-$250
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderately severe, so you should address it soon to avoid poor performance or overheating.
Will this code come back after being cleared?
If the underlying issue isn't resolved, yes, it will likely return.
Why is this code often paired with SPN 117?
SPN 117 relates to the coolant temperature sensor circuit, which may experience issues simultaneously.
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 →