Volvo V70 CEM drowned in rain ! - LeighB
Our neighbour has just a low milegae ex-demo estate. Done 6000 or so miles.
After 4 days he was driving in heavy rain and various strange electrical things happened. Yellow warning appeared on dash and wipers misbehaved - would only work at full speed or not at all. Then the auto gearbox started playing up, and a red urgent warning appeared so he stopped in a layby. He switched the wipers off then on again and the engine stopped and wouldn't restart.
He had to be towed in to the dealers.
They diagnosed a problem with the CEM which had been flooded and wrecked. This seems remarkable, but even worse they told him there were no spares in the UK. He had the impression that a number of V70s had suffered the same fate and all spare CEMs had been used. Told he would have to wait for parts from Sweden.
Is this a known problem?
It seems extarordinary that a fairly normal weather condition can disable a modern car.
Volvo V70 CEM drowned in rain ! - bell boy
think i would reject the car if only owned for 4 days
Volvo V70 CEM drowned in rain ! - Wales Forester
Something wasn't sealed properly for this to happen, and even if the CEM is replaced under warranty there could still be related problems further down the line.
I too would seriously consider rejecting the car.
Has it been bought from the Volvo dealer network?
Volvo V70 CEM drowned in rain ! - stuartl
I would reject the car too. In the late 80's a neighbour of mine bought a brand new Volvo which had an annoying 'squeak' from the dash. After many trips back to the dealer they found behind the dash that two pieces of polystyrene were rubbing together. He argued that all the screws and trim around the dash had been marked and when the dealer refused to replace them he told them to keep the car....and they did! Any decent dealer would have had that car back in there like a shot!
Volvo V70 CEM drowned in rain ! - Red Baron
To me it sounds like a Volvo feature where water got into the electrics and plenty of cross-talk resulted in gobbledygook. Not exactly the dealers fault, but more a design defect. Perhaps they have a Volvo they can pinch one from to get your car going. A completely different car may have other issues.

I'm not familiar with a volvo CEM so what I say below may not apply in this case.

What are the components like in the CEM? Are they sealed or would it be very difficult to get the water out of them. Unplug stuff, open it and take a look inside. If the water ingress is very recent then little or no corrosion will have started on the solder joints and copper tracks. You may be able to fix it by drying it out. I have tried exactly this on a car I have owned where the electrics started playing up during a drive in the rain. The next morning the battery was flat, but after I had dried it out the 'drowning' never happened again.