Great suggestion, thank you mike1967
i now for sure there is a recall on all Peugeot and Citroen with same prince engines for temp sensor linked to oil light problems i believe are connected as the sensor runs the wrong temp so engine gets to hot for the oil and oil thins with heat etc, i just went through all this with main agents on a c4 with coolant sensor reading below freezing ie -48 all the time and thermostat would not open so car cooked in 10 minutes, turns out it was a bsi issue ie the central ecu that deals with it, main agent told me there were a number of recalls around the thermostat housing and sensor etc,
my fault was the mother of all faults, wiring striped and ecu tested etc new thermostat housing,, this was all produced from the thermostat housing melting inside and going short circuit to positive and shorting out the ecu,, but not the under bonnet one you would think it would, car electronics are getting silly