P0115 means Engine Coolant Temperature Circuit. The computer has detected a general fault in the engine coolant temperature sensor circuit. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0115 means
The coolant temperature reading feeds many systems: warm-up fueling, ignition timing, idle speed, cooling fan control, transmission shift timing and often the dash gauge. A wrong reading causes symptoms far beyond the cooling system, and a real overheat can damage an engine quickly. Confirm the actual temperature with a scan tool or an infrared thermometer before replacing parts.
P0115 symptoms
- Check engine light
- Cooling fan running constantly on some vehicles
- Hard starting, rich running or poor fuel economy
Common causes of P0115
- Unplugged or corroded connector
- Failed sensor
- Wiring open or short
How to diagnose P0115
- Compare the coolant temperature reading with the actual engine temperature
- Inspect the connector and wiring
- Check the reference and ground
Can you drive with P0115?
Short distances; watch the temperature gauge, since fan control may be affected.
P0115 tips
If the cooling fan runs all the time with the key on, the computer may be defaulting to full cooling because it cannot read the sensor; that confirms a circuit fault. Some engines have two coolant sensors, one for the computer and one for the gauge, so make sure you test the one the code refers to.
Will P0115 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0115 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0117 | Engine Coolant Temperature Sensor 1 Circuit Low |
| P0118 | Engine Coolant Temperature Sensor 1 Circuit High |
| P0116 | Engine Coolant Temperature Circuit Range/Performance |
Guides that help
When it is more than a sensor
Most cooling codes end with a thermostat, sensor, fan or leak repair. If the engine overheated badly enough to fail the head gasket or warp the heads, compare a repair against a replacement on our engines page and read engine replacement cost.
Shipping is a flat $80.00 per order to US addresses, with 15-day free returns. Questions? Ask a parts specialist.