P0115 code meaning
Engine Coolant Temperature Sensor 1 Circuit
Powertrain system Generic code P01xx codes Check engine light
What P0115 means
The engine coolant temperature sensor 1 is an NTC thermistor: the control module feeds 5 V through a resistor, and as the coolant warms the resistance and signal voltage fall. Its value drives cold-start enrichment, idle speed, ignition timing, the radiator fan and the release of closed-loop mixture control. Some Ford engines measure cylinder head temperature instead and calculate a coolant value from it. P0115 is the general circuit fault without telling low from high. Today it has largely been replaced by P0117, P0118 and P0119; GM and Ford do not set it in the tables checked. Older or individual systems still use it as a collective code, for example Saab Trionic T5 (1998). The circuit is monitored continuously; when it fails, the module uses a substitute value and many systems run the radiator fan permanently.
P0115 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0115
- Check engine light on
- Poor cold or hot starting
- Radiator fan runs constantly
- Higher consumption, rough idle
- Temperature gauge implausible or dead
Common causes of P0115
- Most likelyConnector corroded or loose, terminal spread
- PossibleBroken or chafed signal or ground wire
- PossibleSensor faulty internally (short, open, coolant inside)
- Less likelyControl module input or 5 V supply faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine coolant temperature sensorEngine coolant temperature sensor wiring
What each part of P0115 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1 | Area: fuel and air metering. |
| 15 | The exact fault in that area. |
What to do next
- Note P0115 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0115
What does P0115 mean?
P0115 means "Engine Coolant Temperature Sensor 1 Circuit". The engine coolant temperature sensor 1 is an NTC thermistor: the control module feeds 5 V through a resistor, and as the coolant warms the resistance and signal voltage fall. It is a generic code, so it means the same on every make.
Is it safe to drive with P0115?
Drive gently and only to a workshop. With P0115 the car can go into limp mode (reduced power) to protect itself.
Will P0115 fail an emissions test?
Yes, it can. P0115 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0115 to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0115 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.