There is not much to go on here but the fact that increasing engine rpm silences the alarm suggests that the oil pressure sensor is reading the normal increase in pressure that is associated with an increase in engine rpm.  So it sounds like the oil sensor is still working but it is possible that the measured pressures are off for some reason.   I think I would err on the safe side and consider the possibility that low oil pressure might be the actual cause of the alarm until you can verify otherwise.   I was getting an alarm on my engine at startup that lasted for several seconds which would stop when I revved the engine and I was of course concerned since this sounded like it could be a serious problem.  So I installed a simple mechanical oil pressure gauge that is mounted to the valve cover and plumbed in via a tee fitting where the oil pressure sensor goes.  I found that on startup that the oil pressure on the mechanical gauge jumped up to 45lbs. immediately but I still got the alarm.  It turned out in my case that the the old oil pressure sensor was sticking and took a few seconds to move to the off position after seeing good pressure.  A good cleaning of the oil ports inside the sensor took care of the problem.  It is hard to know for sure what is going on until you can actually measure the oil pressure.  I hope that you get good news.

Best,

James Alton

Maramu #220