I bought a 2004 Volvo S80 2.5T in September. I own the car "as is". Soon after the electric went haywire. Driving down the road there would be a loud clunk as if running over a pothole. Then the air would go out for a second along with a series of clicking noises. The fan would come on but no air. Then the dash would be out and power windows wouldn't work. The message would read "ABS brake failure, stop safely." I would have to turn the car off and wait to restart.

In October here in Florida it was chilly. The problem stopped. It hasn't done it again until recently. We're now in the 80's and 90's. It's doing it all the time now but only in the afternoon. I was reading the U.K. Volvo forum and a girl described my exact problem. She replaced the CEM. Another user replaced a relay. There's no codes for this other than "system too rich at idle bank 1."

I had someone check it out and he said there is oil on the timing belt. He wants to replace the timing belt, tensioners and pulleys,cam gear, oil pump seals, water pump seals, and clean the throttle body. Estimate 1,000. I'm putting that off because I think this is a separate issue that I really want taken care of now. It is scary to drive with the temperatures rising. I'm afraid eventually it will leave me stranded somewhere.

How do I know if it's a relay or the CEM? Also can I take a CEM out of another Volvo and put it in and that's it? Or do I have to program one? Any advice is appreciated, this car is making me crazy. She's pretty though

 

I assume that this is one of the threads you saw?

Trying to get to the bottom of my "mystery" problems... CEM failure in with heat...

They talk about installing heat sinks and a fan. Being an ex IT geek myself I can say that I agree with the responder that added cooling can help things along greatly assuming that the circuits aren't actually fried. I don't know if I would be cracking open the module to add on extra heat sinks. That black box is pretty pricey to be carving it up. I would consider adding an under dash fan to help with cooling as a stage one cheaper fix. One low RPM 80 MM case fan, a vampire clip to accessory power, and a solid ground should do it. If you're interested in trying it I'll poke around and see what fits in my S60 and XC60. Hopefully the space is about the same on an 80. If it doesn't work you can always remove the clip, tape the connection back up and toss the fan being out on 20.00 or so instead of hundreds.

 

Thank you! I just received a 12V computer fan. I ordered it from newegg.com.. Walmart didn't have any and I got a skeptical look from the kid in electronics when I told him it was for my car My uncle is a plumber and a handyman. He says he can put it in.

As of now it hasn't shut off during the afternoon in days. I took the outer panel off under the wheel and I put the air on full blast at my feet. So I'm pretty positive this is an overheating issue with that CEM. Only drawback to that is that I can't listen to any strange noises coming from the car if there are any.

It's been idling rough on occasion. Sometimes check engine light comes on. Goes away again. When I go to slow down it throws forward a little. Sometimes when it's doing this, it takes a few tries to start. So my next move before I have the throttle body cleaned and timing belt kit changed is to give it a tune up. I'm going to order genuine Volvo spark plugs (mine takes 5) and see if that makes a difference. If not I'll keep working on it, ignition coil. Wires. Very annoying when there's no code except "Rough Idle Bank 1".

Thanks for the help

 

The issue of the oil soaked timing belt also definately needs attention ASAP or it may break resulting in bent engine valves and cylinder head damage.
It is unfortunate that you have 2 rather important issues to contend with simultaneously.

 

I removed the panel underneath and laid a 12v fan from the cigarette lighter on the floor. The fan was medium sized. This worked for a few years during the summer months. I had to let the hot air escape and let the fan run for a few minutes before turning the car on. As long as the temperature read under 90 degrees Fahrenheit, I was in the clear. Over 90 was danger zone and car’s electric could cut out at any moment. Very stressful but thankfully it was only a threat for a few months out of the year.

The timing belt and all was replaced for 700.
I recently traded it in for less than 1,000 dollars. It had a crack in the engine mount and the unresolved issue. I financed a 2019 Nissan kicks. My first new car. I’m so happy. I know it’s an old thread but thanks for taking the time to respond!