P2559: Engine Coolant Level Sensor/Switch Circuit High
What to do
The car will drive normally; what has gone is the low coolant warning. If anything has been done under the bonnet recently, mention it — the connector on the expansion tank is brittle and easily knocked off during unrelated work, and that is a two-minute fix rather than a new sensor. Meanwhile check the level yourself on a cold engine now and then, because the dashboard cannot do it for you until this is repaired.
What this code means
The coolant level circuit reads above its valid range — an open circuit, a disconnected connector, or a short to supply.
An open circuit is the commonest finding, and the expansion tank connector is the usual place: it sits in a hot, damp corner of the engine bay and its plastic becomes brittle with heat cycling, so it breaks when someone leans on it during unrelated work. A coolant level code appearing shortly after any job in that part of the engine bay is very often a connector left unclipped.
As at P2556, the practical consequence is the loss of the low-coolant warning rather than anything the driver will feel.
Likely causes
Start here
- Open circuit in sensor wiring · moderate
- Disconnected sensor connector · easy
- Faulty coolant level sensor · easy
Less common
- Corroded or loose connector · easy
- Wiring shorted to voltage · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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