Evanio says there is mileage of 100000 on the clock so not km's, if levels are ok, no signs of leaks etc then this is most likely a sensor fault, to confirm for sure you need diagnostic equipment which most mechanics would have, suggest you get a diagnostic readout of the faults on the car done by the seller or you arrange it and take it from there.
The dealer may have some responsibility but was it a main dealer or an independent sole trader, my view would be that getting a warranty on a car that has covered 100k miles would be impossible to expect, I reckon you bought the car as is, that car was I expect good value at the price and you accepted the risks associated, that said it is not a big issue to resolve.