P0115 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Safe to drive (short-term)
P0115 on a BMW means the ECU has detected a general fault in the engine coolant temperature (ECT) sensor circuit. The ECT sensor is a thermistor whose resistance changes with temperature, telling the ECU how warm the coolant is so it can adjust fuelling, ignition timing and the cooling fan. A fault here usually points to a failed sensor, damaged wiring or a bad connector. Repair typically costs 40 to 180 EUR depending on whether you DIY or use a shop.
- Severity
- Moderate · Cooling System
- Typical repair cost, all makes
- €12-€180
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your BMW and Skanyx tells you what P0115 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0115 mean on a BMW?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the BMW models that log P0115.
BMW 3 Series
2006-2024
On BMW 3 Series engines the coolant temperature sensor sits in the cylinder head or, on many models, in the electric coolant pump or thermostat housing. The sensor and its connector are reliable, but plastic cooling components age, so verify the live reading before condemning the sensor itself.
What causes P0115 on a BMW?
Beyond the generic causes listed on the main P0115 page, these are the patterns noted for BMW models:
Connector terminal fretting causing intermittent signal loss
: BMW 3 Series
Sensor failure alongside aged plastic thermostat housing
: BMW 3 Series
How to diagnose P0115 on a BMW with OBD2
- Read the code and watch the live coolant temperature PID with Skanyx. On a cold engine it should read close to ambient air temperature, then climb steadily to around 85 to 95 C as the engine warms
- If the live value is stuck at a fixed default (often -40 C or 120 C/maximum), that points to an open or shorted circuit rather than a true temperature reading
- Inspect the ECT sensor connector for corrosion, bent pins, or a loose fit, and check the wiring for chafing or rodent damage
- Measure the sensor resistance with a multimeter and compare against the manufacturer resistance-versus-temperature table
- Check coolant level, because a low level can leave the sensor tip in air and skew the reading
- If the sensor and wiring test good but the fault persists, check the sensor ground and signal continuity back to the ECU
How much does P0115 cost to fix on a BMW? (EUR)
Estimated repair costs for P0115 in EUR, compiled across makes. Expect BMW parts and labour towards the upper end of each range.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace coolant temperature sensor (DIY) | €12–€45 | €0–€0 | €12–€45 | Easy |
| Replace coolant temperature sensor (shop) | €12–€45 | €40–€100 | €52–€145 | Easy |
| Repair wiring or connector at sensor | €5–€30 | €50–€150 | €55–€180 | Moderate |
| Diagnose and trace circuit fault (shop) | €0–€0 | €60–€120 | €60–€120 | Professional |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0115
These codes are often seen alongside P0115 or point to related issues, on any make:
Looking for the full P0115 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0115 guide