Stop engine oil pressure!!!!!

[Mikedd]

I started up the 01 X4.4 this AM and it was a rougher than usual start and the message "stop engine oil pressure" comes on. Before I could shut it off the engine smoothed right out. Shut the car off, checked the oil (full and it has been since last change 30 days ago). re started and runs like a top again. The SES light is on now but it runs fine, if anything it idles smoother? One thing I noticed is that there is a a whine sound for the first 30 seconds on start (like a fan ). I have seen this code before about 6 months ago after washing it. No issues till today. My code reader is lent out so i thought I would throw this out there in case anyone has had the same set of circumstances.

Thanks