Volvo: 1999 S80 Stop Engine Immediately - No Oil Pressure message, low oil pressure, oil cap

Question
My 99 S80 has 120,000 miles.  I was getting a "Stop Engine Immediately - No Oil Pressure" message and had car towed to a mechanic.  They fixed a sensor first, then gaskets, then thought it was the oil pump.  Long story short, they still don't know what the problem is.  We are considering bringing it to Volvo for them to try to diagnose.  Any ideas or suggestions?

Answer
Joanne,
Boy good question. Did anyone take an oil pressure reading using a gauge? That is a start to see if it is low. Now the seals on the oil pick up tube in the pan the sump, get dried out and that causes low oil pressure. So the pan comes off and new seals are installed and all is good. If the pump get replace and not the pick up seals then there is still low pressure. If your shop is replacing the pump make sure they also do those seals. Or you can still have the car taken to a Volvo shop and tested... Just a note the dried up seals are a common problem and possibly the one you have. So if the pressure is low and while the car is running you see airrated oil when you look into the oil cap area I would replace the pick up seals. Hope that is all clear and understandable...