P0115: Engine Coolant Temperature Sensor Circuit Malfunction

Short answer: P0115 means “Engine Coolant Temperature Sensor Circuit Malfunction”. It is a standard OBD-II code, so the basic meaning is the same on every car. Below is what it means on each of the 8 cars we cover, with a link to the full page for each car.

Standard OBD-II code Same meaning on all cars (SAE J2012).

P0115 on each car

Symptoms

1. Check engine light on
2. Vehicle may be hard to start
3. May blow a lot of black smoke and run extremely rich
4. Engine may want to die or backfire in tailpipe
5. Engine may run lean and increased Nox emissions may be apparent (Requires gas analyzer)
6. Cooling fans may run all the time when they shouldn't be, or not at all when they should be

Likely causes

1. Usually the cause can be traced to a bad
2. ECT sensor
3. Wiring or connector damaged at sensor
4. Open or short in reference or signal circuit
5. Open or short in signal circuit
6. Bad PCM

What to check, in order

1. Read the code and freeze-frame data with an OBD-II scanner
2. Check the connector and wiring of the part named in the code
3. Test the part with scanner live data or a multimeter, using the values in the repair manual
4. Fix the cause, clear the code and test-drive

Causes and checks above are the general meaning. The exact test steps and values differ by car: open your car’s page.

All fault codes