P2559 indicates that the engine control module has detected a voltage signal from the engine coolant level sensor switch that is higher than the expected range. This usually points to a short to voltage, a faulty sensor, or a wiring/connector issue rather than an actual low‑coolant condition.
The sensor itself may have an internal short to voltage, causing the PCM to read a persistently high signal.
Damaged insulation or a chafed wire can allow battery voltage to feed into the sensor circuit, producing a high voltage reading.
Poor connection at the sensor or PCM connector can increase resistance or create a false high voltage signal.
A rare internal fault in the PCM’s coolant level sensor circuit can cause a high reading; this is considered only after sensor and wiring are verified good.
No. PCM failure is uncommon for this code; most cases are due to a faulty coolant level sensor, wiring short, or connector issue. Replace the PCM only after those components have been tested and found good.
Low coolant itself does not trigger a high‑voltage signal; however, if the coolant level is actually low and the sensor is stuck reading high, the warning may be misleading. Always verify the actual coolant level first.
If the coolant level is correct and there are no signs of overheating, short‑term driving is generally safe, but the fault should be repaired to avoid missing a genuine low‑coolant condition.