P0115 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.
DTC/P0115·Toyota
P0115 on Toyota: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Toyota
P0115 on a Toyota 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.
Repair cost on Toyota€11 - €162
What does P0115 mean on a Toyota?
Toyota Corolla
2005-2024Toyota coolant temperature sensors are durable and P0115 is uncommon, but when it appears the connector terminals can corrode, especially in humid or salted-road climates. The sensor is inexpensive and accessible near the thermostat housing on most 1.8 and 2.0 engines.
What causes P0115 on a Toyota?
Beyond the generic causes listed on the main P0115 page, these are the Toyota-specific patterns we see most often:
Toyota CorollaConnector corrosion at the ECT sensor in humid climates
Toyota CorollaAged thermistor drifting out of range past 200,000 km
How to diagnose P0115 on a Toyota with OBD2
Follow these steps to pinpoint the root cause of P0115:
- 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 Toyota? (EUR)
Estimated repair costs on a Toyota (Toyota parts and labour typically run 10% below the average for this code).
Prices estimated as of May 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0115 on Toyota
These codes commonly cluster with P0115 on Toyota vehicles:
FAQ: P0115 on Toyota
Can I drive with a P0115 code?
For short trips, usually yes. The engine runs on a default temperature value, so you may get worse fuel economy and rough cold starts. The bigger risk is that the temperature gauge may be wrong, so you lose your warning for genuine overheating. Fix it soon and watch the temperature in the meantime.
How much does it cost to fix P0115?
The sensor itself is cheap, usually 12 to 45 EUR, and replacement is a simple job on most engines. A DIY fix can be under 50 EUR. A shop replacement runs roughly 60 to 150 EUR, and tracing a wiring fault costs more because of the labour involved.
Where is the engine coolant temperature sensor located?
It is usually threaded into the cylinder head, thermostat housing, or a coolant passage near the top of the engine, so its tip sits in the coolant. Many engines have two sensors, one for the ECU and one for the dash gauge. Check a vehicle-specific guide for the exact spot.
Is P0115 the same as a thermostat problem?
No. P0115 is an electrical fault in the temperature sensor circuit, not a cooling problem. A stuck thermostat is more likely to set P0128 (coolant below thermostat regulating temperature). They can feel similar from the gauge, so confirm with live data before buying parts.
Looking for the full P0115 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0115 guideSkanyx · Toyota
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