P01E4
Engine Coolant Temperature Sensor 3 Circuit Range/Performance
ECT sensor 3 reading implausible. The engine coolant temperature sensor feeds warm-up enrichment, fan control and closed-loop entry — a stuck-cold reading keeps the engine in open loop and rich forever.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: easy
Symptoms
- Check engine light on
- Cooling fan runs constantly or not at all
- Cabin heater weak or excessively hot
- Possible long warm-up time or hard cold start
Common causes
Ordered by how often each turns out to be the cause.
- Sensor reading driftedCommon
- Sensor element aged beyond calibration windowLess likely
- Sensor mounting loose - signal dampingLess likely
Parts involved
- ECT Sensor 3
P01E4 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.