P0115 — Engine Coolant Temperature (ECT) Circuit Malfunction
Drive with caution — fix soon.
What P0115 means
This code means the engine computer detected a problem with the coolant temperature sensor circuit, which tells the system how hot your engine is running. Common fixes are replacing a faulty ECT sensor or repairing damaged wiring or a corroded connector. It's a common, generally affordable repair, but it matters because the coolant signal helps protect your engine from overheating.
Common symptoms
- Check engine light is on
- Cooling fans running constantly or not at all
- Hard starting or rough idle when cold
- Reduced fuel economy
- Temperature gauge reading incorrectly
Common causes
- Faulty engine coolant temperature sensor
- Damaged or corroded wiring in the ECT circuit
- Loose or unplugged sensor connector
- Open or short circuit in the sensor wiring
- Low coolant level affecting the sensor reading
Typical repair cost
$100 – $300
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0115 code?
For short trips usually yes, but you shouldn't rely on it for long. Because this sensor helps manage cooling and overheating protection, a bad reading can hide an actual overheating problem. Watch your temperature gauge and get it checked promptly.
How much does it cost to fix a P0115?
Most repairs land between $100 and $300. The sensor itself is inexpensive, but its location can make labor vary. Wiring-only repairs may cost less than a full sensor replacement.
Is a P0115 code serious?
It's moderate in severity. The repair is usually simple, but a faulty coolant signal can affect engine protection and fuel mixture. It's best not to leave it unfixed for long.
Can a P0115 cause my engine to overheat?
Indirectly, yes. If the computer can't read the true coolant temperature, it may not turn on the cooling fans when needed. That's why it's important to verify your actual coolant level and temperature while the code is present.