Not properly qualified to answer but that has never stopped me...
Either the Overheat Thermostat is faulty and saying overheat when there is no overheat or...
The Overheat Thermostat is working correctly in which case the pump may not be circulating water quickly enough to dissipate the heat around the system.
As ever people continue to "rubbish" the Suprima PCB and this may be the culprit.
I can not imagine the pump being wired incorrectly as the cause of your problem - not after 4 years.
Peccavi
December 2008