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DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P2559

P2559Engine Coolant Level Sensor/Switch Circuit High

P2559 means the engine control module (ECM) sees the coolant level sensor or switch circuit reporting a voltage higher than expected, which usually indicates an open circuit or a sensor signal that is out of range. The ECM monitors this circuit to warn the driver when the engine coolant level drops too low, so a high-voltage condition can be a false alarm caused by wiring or a failed sensor rather than an actual low coolant level.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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