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

[95SE]

MY '04 XC70 196,000 miles or so

I purchased the car 3 years ago. About 1 year in I made a long trip in summer that was easily 4-5 hours of driving. About 2 hours in the car shut off while I was going about 70mph on the NJTP. It immediately came back on but was in 1st gear so the car slammed. Different warning lights came about such as SRS Failure and Rear Left Door Ajar. Honestly I thought It a big pot hole, but realized that the cruise was now off and the fog lights were off... well within a minute or two it happened again, and it happened a couple of more times before I could get off the highway to a safety. We let it sit and cool thinking it just needed a rest... and it was Sunday night and we were still 200 miles from home. So I started pulling fuses. It turns out that the one for CEM did it, I was able to start the car again and it was back to "normal". We made it another 50 miles or so before problems returned. We kept up this fun pattern until we got home. Parked the car and the next day and for quite a while there were no problems. I researched and talked to Volvo specialists, but no answers. The codes they pulled were random and caused by the sudden shut off and turn back while doing 70mph. I don't blame them but they wanted to keep the car for diagnostics, I don't like to just let bills add up so I denied it and figured whatever, I just won't drive long distances. Because of research I had my alternator tested and also changed the battery. Problems would return on really hot days and extended driving times.

Other symptoms that came up: Brake Failure, Pull Over Safely, no dash lights, wipers turning on with being switched on, interior lights not functioning correctly, power windows not operating correctly, check engine light, and probably others.

Well a common theme came up in the interwebs, the CEM. I dropped the CEM down from the hanger, turned on the car with the heat to the floor and let the car idle. The problem showed up in ten minutes. Does this prove it is the CEM? IDK, but this is what XEMODEX said to do to diagnose the CEM as the problem. I shipped it out today to them so that they could transfer all of my data and software to a brand new one that has a better heat sink (cooling ability?). They said that they see this problem many many times a year. I hope that my issue will be resolved, it is scary as heck when the car turns off while driving and it can't be that good for the tranny.

Here and there I would find posts on the web about this issue but I would expect more. I imagine that most Volvo owners are not fix it yourselfers for one and that the lack of common language hurts. It took me a year or more to come across the word CEM, I had no idea to search with that term and was using the term CPU or computer instead...

Oh well, I will follow up when I get it back and run the same heat test on the new one. Side note is that my friend with 04 S60 has the same symptoms.

This will cost me $600 after shipping, although not cheap, if it fixes it I am happy. My other option was trying a Volvo dealer which I imagine would have been in the 1200-1600 range?

To me this feels like a strange post, but I am doing it to hopefully help others with same issue. The problem seems random and related to long driving trips but in actuality it is just a heat issue, I imagine the CEM gets hot if the car is running for hours and I can't say that I blow A/C on my feet which may have helped I guess.

Please post in here if you have the same problems.

I understand that the CEM issue with 2005 and 2006 is due to clogged water drainage channels that result in water getting on the CEM and corroding it. I am not sure but what is different about those years, but that issues is specific to them.

[ifnt420]

Sounds like a common MY04 CEM issue.
Check out Forksters post: http://www.volvoxc.com/forums/showth...r-on-the-fritz

Good luck and keep us posted after Xenonmod fix!

[Forkster]

Strange thing that the 2005+ have heat sinks on the CEM...yet Volvo claims there is no issue with the 2001-2004 CEM modules overheating.

So, what the rest of you can do is spend hundreds of dollars on a rebuild or buy a $20 case fan and have it blow on the CEM casing. And don't drive with the cabin of the car hot - keep it cool below 22 Celsius or 72F. I choose the $20 fan option after determining it was a simple overheating issue. All it needed was a way to keep cool...

If the CEM overheats, it is the bridge between the low and high speed buses in the Volvo. It's why your dash will do dead, your door will alarm that it's open, why your transmission will go into limp mode, you'll get all kinds of failure messages...is because the CEM is loosing its ability to keep the bridge going cause it's too hot and all of the other car computer systems will start acting up with a lot of really crazy messages. And no two Volvo's will fail the same way...

I found a neat computer case fan that is on a snake-neck mount that allowed me to position it exactly over the CEM and i then wired it to my front 12V adapter fuse. No more issues going on a year now.

[Allen]

Nice one Fork.

[95SE]

Great fix Forkster! I never came across your thread, bummer. I posted a thread on here too, sometime ago. I had this idea too to put a fan on it, but I really wanted to be more sure of the fix because I bought the car to travel in. I don't doubt that your fan mod is working. Is there a cooling fan already in there, your thread talks about one for a bit but nothing seems to pan out of the conversation.

[JRL]

I never had an issue but I also like it very cold
Also remember the 05 and newer Volvos have a different electrical system!

[bushcamper]

I found a neat computer case fan that is on a snake-neck mount that allowed me to position it exactly over the CEM and i then wired it to my front 12V adapter fuse. No more issues going on a year now.

Thank you Forkster!

can you please provide a picture and/or partnumber of your fan-solution. Seems this is the solution for our V70 MY03 problem as well:

After driving on france autoroute for hours - it was already afternoon and temperature around 30°C -, sowewhere north of Clermont Ferrand, suddenly at highspeed there was a thump from the front. I stopped, everything seemed fine, started again and some KMs later it happened again and then a thrid clunk from the transmission as the auto gearbox forced a change down to limp mode. Seconds later the whole electric system was dead. After engine-restart there were lots of warnings in the bordcomputer-display, among others the hint to stop immediately because the engine-temperature being too high, and yes, the temperature-gauge was in the far right red area.

That definetively was a fault of the electonic system. To make sure, we drove to a nearby garage and they checked the cooling system and the temperature: everything fine, but the warnings were stil there. We decided to drive on...
Some 50 KMs later it happened again: 3 thumps and all electonic dead.
In limp mode we drove another 50 KMs for a place to stay for the overnight. The next day we drove home without any problems at all. Outside temperature never made it up higher than 20°C

I already guessed, that we have an hot temperature related problem with the CEM, since we already had that before, but not while driving. We had a complete loss of the CEM in hot weather on our last three trips to France, always at the end of the driving when we stopped at our final destination. After resetting the CEM (fuse out and in) everything was fine again (of course we never drove on).

Any help is very appreciated.

Best wishes
Stefan

[piusg]

I came across this fix after I'd already implemented exactly the same one myself for my own XC.

I have a 2004 XC70. My sweetheart and I were driving at night through a secluded part of Vancouver Island last year when the first failure hit. Only in our case, it was 35 degrees Fahrenheit.

After a loud, jarring bang, all the cabin lights illuminated, immediately followed by a "Left Rear Passenger Door Open" message on the MFD. After another few miles, the dash failed completely. Only a 30 minute cooldown allowed the vehicle to operate normally or indeed even start. A terrifying problem to be faced with in the middle of nowhere.

After much scouring the forums and some empirical experimentation, I determined that this is a problem with the CEM. The main culprit was the cabin heater, venting through the foot pan air directors, which enveloped the CEM in a stagnant bubble of superheated air that caused the hapless module--already blessed with notoriously bad airflow and excessive shielding--to overheat and fail.

Being an IT guy, I've repaired many computers with overheat problems over the years, and the XC70's CEM is no different than any other overheating computer. After removing the CEM, I removed the top of the chromed processor shielding box and elected to leave it off of the CEM. Utilizing forceps and patience, I installed self-stick copper heatsinks--the kind normally used to cool memory modules in high-end gaming rigs--on the processor and every glue chip I could get to. I trimmed the black perforated plastic off of the top using a rotary cutting tool to increase airflow even further. I then affixed a 12v PC chassis cooling fan to the top with tie wraps, such that it constantly blasts circulated air across the planar and heatsinks, and supplied power to it by wiring it into directly into the accessory circuit.

I've been pounding on it for the last four days in a winter shakedown roadtrip, through brutal Pacific Northwest winter driving conditions in freezing rain and snow, blasting the heater into the footwell for hours at a time. My XC70 has performed flawlessly. The cooling fan on the CEM, despite its size and relatively rapid RPM, is only audible upon vehicle start and even then only barely.

Instead of paying a zillion dollars for a replacement CEM from Volvo, or $1,000 for an Xemodex refurbishment of my existing CEM, I solved this otherwise terrifying electrical gremlin with about three hours of elbow grease and less than fifteen bucks.

[bushcamper]

I am glad, you fixed that issue!
Our V70 is still fine: no problems since I implemented that fan-solution in 10/2013.
You might want to have a look here (in german):
http://www.motor-talk.de/forum/my03-...l#post38541865

Rgds
Stefan

[Tucu]

I have had the same problem with my XC70 2004 for a year now. Winter time no issues at all, now summer comes and the car goes crazy. Exactly as described. To give @Forkster theory a try I turn my AC (feet only) almost full blown and surprise surprise, no crazy behavior to report. Now I would love to see how toy installed the fan. Your input is much appreciated!!