We have owned 4 700s, 3 850s, and 2 xc70s. As a family, we have driven over 800K in those cars.

I have our cars serviced by a dealer, and they never replaced more than one item (if That) when we had a problem with these cars.

Once, the dealer even took the anti-lock unit out of our service writer's car to see if mine was defective - the anti-lock would go out if I went over a certain kind of bump - it would always reset when the car was shut off and started for the next trip. It only happened about once a week or so.

I suggest that you take the car to a dealer for evaluation - most new car dealers only charge one hour's labor for troubleshooting, although I found that my dealer charges $175 for a full scan on an XC70.

BTW have you tried disconnecting the battery for 5 minutes or so?

Doing that cured a problem that I had with my TPS sensors and my remote key. A TPS low tire warning left overnight would lock me out of the car! Evidently rebooting the computers fixed my car.