It may indeed be a CEM water ingress issue, you may have a look at it see if there's water marks on the box - look up on Youtube
It can be repaired by Xemodex
There is also a computer called ECM, located in front of the power steering reservoir. Hopefully not faulty as this has to be replaced with a new unit$$$$$ from Volvo. This one can fail if it overheats, usually because the small cooling fan at the back of the box has failed.