P0115
ECT Sensor Circuit Malfunction
medium
i Description
The Engine Coolant Temperature (ECT) sensor circuit has a malfunction. The ECT sensor tells the ECU how warm the engine is, affecting fuel mixture, ignition timing, and cooling fan operation.
? Common Causes
- Faulty ECT sensor
- Damaged wiring or connector
- Low coolant level exposing sensor
- Corroded connector pins
! Symptoms
- Check engine light
- Incorrect temperature gauge reading
- Poor cold-start performance
- Cooling fans running incorrectly
- Rich running when warm
# Diagnostic Steps
- Check coolant level
- Test ECT sensor resistance at known temperature
- Inspect wiring and connector
- Compare ECT reading to IAT at cold start (should be similar)
⚙ Typical Fix
Replace the ECT sensor. Top up coolant if low.
Parts Needed
ECT sensor, Coolant (if low)
Estimated Cost
$30-$200
↔ Related Codes
Q Frequently Asked Questions
You can drive, but the engine may run rich (wasting fuel) because the ECU may assume the engine is always cold. Also watch your temperature gauge — if it is not working, you could miss overheating.
Yes. ECT sensors are inexpensive ($15-$40) and usually easy to access. You may need to drain a small amount of coolant.
Parts: $15-$40. Mechanic labour: $50-$120.
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