P2557
Engine Coolant Level Sensor/Switch Circuit Range/Performance
The coolant level sensor is electrically intact, but the readings are implausible — for example a level that does not move at all over many drive cycles, or jumps that cannot match real coolant loss. Often a stuck float, contaminated electrode or air-locked sensor.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: easy
Common causes
Ordered by how often each turns out to be the cause.
- Stuck floatCommon
- Trapped air around the sensorPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- Coolant Level Sensor
- Cooling System
P2557 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.