If its not electrical id go for oil pressure relief valve, Ive seen these stick in the housing from time to time after they get a little scored or sludgy.
Easy to remove in situ just take out the oil temp switch on the pump and the valve, spring and a little oil should drop out, note the order and direction of the parts!!!
Polish the exterior of the valve plunger doodah with autosol or other metal polish and clean it thoroughly.
Refit then sit back and relax as the oil light comes on yet again..
