Engine Coolant Temperature Sensor 1
This code indicates a problem with the Engine Coolant Temperature Sensor 1 reading.
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 1 is supposed to monitor how hot the engine coolant is. If it's not working right, the computer can't tell if the engine is getting too hot or not, which can lead to overheating.
What the computer is actually seeing
The engine control module (ECM) expects to see a voltage signal from the coolant temperature sensor that's proportional to the coolant temperature, typically a range from 0.5V (cold) to 4.5V (hot).
What a healthy reading looks like
Coolant temperature should be between 180°F to 220°F when the engine is operating normally; sensor voltages should be between 0.5V and 4.5V.
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 connectors going to the Engine Coolant Temperature Sensor 1 for damage or corrosion; repair as needed.
- 22. Test the temperature sensor with a multimeter; it should read a resistance that varies with temperature (e.g., 2.2k ohms at 68°F). If the resistance is out of spec, replace the sensor.
- 33. With the engine warmed up, verify the signal voltage at the sensor connector; it should be around 2.5V. If it’s not in range, check wiring continuity back to the ECM.
- 44. Look for coolant leaks that could affect sensor performance; repair any leaks found.
Common causes
- Faulty engine coolant temperature sensor
- Damaged wiring or connectors
- Corroded sensor terminals
- Coolant leaks affecting sensor readings
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It's best to fix this issue soon. If the engine overheats, it can cause significant damage.
Will this code come back after clearing?
If the underlying issue isn't fixed, the code will likely return.
Why does this code sometimes pair with SPN 125?
SPN 125 indicates a problem with the coolant level sensor; both can show up if there's a coolant leak or overheating issues.
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