Featured Insufficient Engine Oil Pressure in Prius 2013

I have 2013, 1.8 Prius, 2 months back I encountered the error of insufficient engine oil pressure, I checked the engine oil, it was ok. I get it checked by the mechanic and he told me that the engine oil needs to be changed and he will wash the engine too, after getting the engine washed and oil changed the car was running smoothly, bus during the last 2 months the same error just blinks and then goes off, now again when ever I accelerate the car " insufficient engine oil pressure error" appears and then disappears after 30 seconds to 1 minute, kindly advise what to do ? the engine oil is up to the mark , I have even replaced the Main computer of the car, but still the error appears, there is no leakage, dip stick shows full engine oil, I don't know what else is to be done now ? the car is running smoothly but I am just too sick of this error. kindly guide me