P0115

Engine Coolant Temperature Sensor 1 Circuit

Fuel & air metering Generic OBD-II High

What it means

P0115 means the computer sees a problem in the engine coolant temperature (ECT) sensor circuit. That reading is used to set cold-start fueling and control the cooling fans, so a fault can cause hard cold starts, rich running, poor economy, and mismanaged fans — occasionally leading to overheating if it's ignored.

High

Can I keep driving? Usually drivable, but a bad coolant-temp signal can cause hard cold starts, rough running, and poor economy, and it can interfere with fan and overheating protection — fix it soon.

Real-world scan data

Seen in

3,716

scans in the past year

Found in

0.6%

of scans

1.1%

of scans that found faults

Appears alongside · share of P0115 scans

P0110in 34.7% of scans

P0683in 29.9% of scans

P0100in 22.7% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Hard starting when cold, or rough running until warmed up
Poor fuel economy (engine may run rich)
Cooling fans running constantly or not engaging

Common causes

Most likely first

Faulty engine coolant temperature (ECT) sensorLikely
Corroded, loose, or damaged connector at the sensorCommon
Open or shorted wiring in the ECT sensor circuitCommon
Low coolant level leaving the sensor uncoveredLess often
Rarely, an ECM/PCM faultLess often

How to diagnose & fix

Work through it in order

Read live data and compare the coolant-temp reading with the intake-air temp on a cold engine — they should be close at cold start.
Inspect the ECT sensor connector for corrosion and a secure fit.
Check the signal and ground wires for opens and shorts back to the ECM.
Measure the sensor's resistance against spec across temperatures; replace it if out of range.
Confirm coolant level and condition. Clear the code and re-test through a full warm-up.

FAQ

Quick answers

Is it safe to drive with P0115?+

Short-term, usually yes, but the engine may start hard when cold and run rich, and the computer may mismanage the cooling fans. Because that can lead to overheating, don't leave it unaddressed.

Can I just clear P0115?+

It will return until the sensor or wiring is repaired. The ECT signal is used constantly for fueling and fan control, so the fault reappears quickly.

Read & clear P0115 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX