P1285 is for engine overheat temperature detected by the cylinder head temperature.
Possible causes are sticking thermostat, internal leak of the headgasket or intake manifold, external leak, faulty water pump, cooling fan, or restricted radiator.
The first step will be to do a cooling system pressure test to check for external leaks as well as loss of pressure and no external leak indicating either headgasket or intake manifold.
If it holds pressure, then the water pump, thermostat and radiator will need to be tested.
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