While driving my xc90 5cycle no turbo the other day I had the "low oil pressure" message come on. I pulled over right away and turned off the engine. I heard no valve noise or knocking. In fact the car was driving flawlessly. I had the oil changed two days before. I called my mechanic and they realized they put only 5 qts oil instead of six. So they drove out and put in the quart. I started it and the light went off. I drove the 15 mins to their shop and they checked it out, no leaks or issue. I said goodby and left. 8 miles down the road, same issue. I called them and they said to bring it back. I again, started the car and there was no message, this time after only a few mins the message came back on. So I called a tow truck. According to my mechanic who has worked on my volvo for the last 5 years, they think it was a bad oil filter. They put on a new high quality filter and drove the car under varying conditions for 20 miles and the message did not come back. They could not locate the oil pressure sensor so they didn't actually test the pressure....

Does anyone know where the sensor is so they can test the pressure? I don't feel comfortable with just changing out the filter.

 

Should be on the front of the motor on the passenger side of the oil filter housing.

 

Would a break assist vacuum pump leak cause a low oil pressure message?

 

No, there's no relationship to the vacuum system. The oil sensor does not use vacuum assist.