this is what the Oil Pressure Sender looks like (also known as a VDO Pressure Sender).


I have this exact same problem, i changed the Sender unit to a brand new Ford Item £103 and still didnt change it, but i have an oil pressure problem at the mo, which is going back in to be looked at, so thinking it may be something to do with that, but wont find out until the pressure is sorted out.

I will keep you posted mate if mine gets sorted and what the cause is.