Thought I'd try the experts here...

I have a 2004 XC90 that has suffered an intermittent electrical problem for years, and Volvo never was able to figure it out while it was under warrantee, despite numerous trips to the dealer and wholesale replacement of modules in a seemingly random attempt to fix the problem. I’ll try to describe the problem the best I can, but the video here probably shows it best - http://youtu.be/cfcUr2LCdo4

I used to only have the problem on longer drives (several hours), but now it happens within 30 min or so, making the car almost unusable. Since it’s no longer covered under warrantee, I am looking at trying a few things myself to see if I can fix it and want to run it past the experts here.

Here’s the problem. The engine, lights, dash – almost everything – will “glitch” – that is, turn off then on quickly. You can hear many relays click when this happens. Once it does it once, it will do it again within a few minutes and eventually (within 4-5 min) the car will go into limp mode – no lights work (except headlights, perhaps brake lights, unsure) and you have to pull over, shut down and wait 10-15 min for it to cool down before it works again. The only thing that stays lit is the AC quadrant in the center console (see video for progression). Volvo believes it’s a module on the CAN bus that’s hanging up the bus causing other modules to “reset”, but was unable to figure it out.

Within the past month this has gotten worse, and twice has “locked-up” the car to the point that I had to disconnect the battery to get it back (nothing operational; locks, windows, starter, etc).

Some observations after living with this for years… It appears to be heat related, it happens more frequently when it’s hot, or when the engine is working hard, producing more heat. Because of this, I think it’s a module in the engine compartment, perhaps the ECU? Not sure what other CAN bus connected modules there are in the engine compartment. I am trying to figure out a plan of action, I am thinking of installing a remote thermometer in the ECU housing to track the internal temperature and see if the problem happens at a particular temp. If so, I’ll look at some ways to cool the box – perhaps a thermoelectric chiller installed in the cover? Is there already passive cooling that is perhaps clogged?

More drastic would be to pull the boards and inspect for bad capacitors (there were many around that timeframe), or perhaps do a hot oven PCB reflow of the solder if I suspect bad solder joints. I am an electronic hobbyist and have built my own PCB’s for microcontroller projects, so I am comfortable doing this.
Or, maybe I buy/build a CAN bus analyzer and sit it on the bus recording activity and find the smoking gun that way? I am leaning towards solving the heat problem since that’s what it appears to be...

Suggestions? Is this a known problem? Is there ECU cooling that I should look at first? Or perhaps I am looking in the wrong area? Any help appreciated!

SteveL

Hi Steve, I have exactly the same problem on my 2004 XC90 - I bought it secondhand in 2009 and have been living with it since. I can't even really sell it. Might you have solved it at all. I have spent too much already trying to solve it.

Peter

The post you responded to was resolved in 2012. Did you read Steve's last post?

"Just to recap - I removed the CEM module from under the dash, removed the approx 2"x2" silver metal cap on the board (which is an Electro Magnetic Interference, or EMI shield) and placed a heatsink out of this kit on the MCU/CPU (biggest chip there)http://www.amazon.com/gp/product/B005EDL2XW/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1

I left the shield off (to promote better cooling) and reinstalled - problem solved!

SteveL "
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Keeping it running is better than buying new

Steve
Did you solve the intermittent fault on your XC90? My XC90, also 2004 plate also cuts out intermittently. Also seems to only do this when it's hot (i.e. last summer a lot and this summer). VERY VERY dangerous as it cuts out when Im driving, suddenly. Always in hot weather a few minutes after I have started to drive it. Several Volvo dealers (and others) have been unable to fix the problem. Very annoying since it still starts up without hesitation and drives perfectly except for this fault, despite having over 130K on the clock. If you or anyone else can help please let me know. (I am currently driving my husbands Merc and the pain in my hips as a result is beginning to stop me sleep!!!!!)

This needs a Volvo scan tool, one that is scanning from engine start to melt down. I suspect the ECU is probably fried, but the connections under the hood to the other modules are also suspect - in otherwords, who knows!

So long as the problem has been documented before the warrantee ran out, and remains unsolved/fixed, Volvo should still repair it for free. Call the Volvo 800 number for verification on Monday.

As to the computer box cooling, yes there is. One the early models, a tube went from the grill to the box and then the air flowed to the fresh air vent system in the cabin. The blower is supposed to draw air from the box and keep the box from baking.
You might try insulating the box. Make sure the blower speed is always turned to some speed (auto is fine).

But call Volvo!
--
Klausc, a Volvoholic

I've had problems with older 740's getting screwy in the heat; some of it was relays that got old & hot, causing the soldered points in the relay to act up once hot, and in one case a clogged sunroof drain ended up dumping water on the computer, corroding it and causing untold screwiness, would run fine, then into limp mode, then stall, then fine. May help lead you to an answer.

Apparently you're not alone:

http://www-odi.nhtsa.dot.gov/cars/problems/defect/results.cfm?action_number=PE10025&SearchType=QuickSearch&summary=true

http://www.aboutautomobile.com/Complaint/2005/Volvo/XC90/Electrical+System

http://www.faqs.org/car/volvo-xc90-2004/electrical-system/

A lot of the evidence seems to point to the CEM - possibly caused by water intrusion.

Just an update to this. I didn't do anything over the winter as, for the most part, the problem was manageable - only crept up after about an hour of driving or so. Now that it's hot again, the problem is back - and way worse. I pulled the CEM today and there was no evidence of water intrusion or damage. After looking at the picture of the XeMODeX replacement (has a heatsink on the MPU) I decided to order up a heatsink that has the right clearance (the ones I had were too tall), and I'll leave the RF shield off to better promote cooling. Heatsink arrives tomorrow and hopefully I'll get it back together, and we'll see what happens!

If this isn't the fix, I did have a sunroof drain leak down the passenger side A pillar some years back - what's on that side that could get corroded from water intrusion?

Steve_L

Do you have the link for that part to fix that you used?

Michael, that is a post from 2012. YOU need to look for a 2X2 heat sink on your own.
--
Keeping it running is better than buying new

Just wanted to give an update - I installed the heatsink on the CPU under the EMI shield, re-installed and it's been working great for the past month an a half! The first real test was the day after I installed it - it was in the upper 90's and I had the AC off, it did glitch once when I was driving up a hill, but hasn't done it since. I have had the AC on on hot days (duh!) and even with the outside temps in the upper 90's to 100 it has been rock solid - no more "glitches".

Just to recap - I removed the CEM module from under the dash, removed the approx 2"x2" silver metal cap on the board (which is an Electro Magnetic Interference, or EMI shield) and placed a heatsink out of this kit on the MCU/CPU (biggest chip there)http://www.amazon.com/gp/product/B005EDL2XW/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1

I left the shield off (to promote better cooling) and reinstalled - problem solved!

SteveL

Steve,

After watching a couple of Youtube segments with the same problem, I wanted to share your fix with others.

I hope you don't mind, but I posted your 'fix' on Matthewsvolvo site --
http://www.matthewsvolvosite.com/forums/viewtopic.php?f=10&t=58006

I also emailed Volvo in NJ and got the following response:

Customer By CSS Web (Klaus Clark) (07/26/2013 05:00 PM)
There are numerous problems with the 2004 XC90, but someone on the Brickboard.com fixed his. The dealer tried and failed. The CEM over heats and causes the lights to go out and put the car in failure mode. A real problem.
The solution is here: http://www.brickboard.com/AWD/volvo/1571641/XC90/xc90_intermittent_electrical_failure_can_bus_related.html

Klaus Clark



CEM

Response By Email (Faye) (07/30/2013 11:08 AM)
Hello Klaus,
Thank you for contacting us. We appreciate your feedback and for taking the time to bring this to our attention. If you are having a problem with your vehicle that you would like me monitor the repair for, please let me know and I will happy to do that for you.
Please feel free to contact me with any other questions you may have.
Have a great day!
Faye
Volvo Customer Care
Volvo Cars of North America, LLC
800.458.1552 ext. 1980






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Klausc, a Volvoholic

Glad to hear the heat sink "fixed" it. Don't feel lonely, there is another youtube video with the same problems:

http://www.youtube.com/watch?v=RxP3sMIL7A0&feature=player_detailpage

The drain tubes??? If water gets the to the CEM, won't it be toast?
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Klausc, a Volvoholic

Sound's plausible! Does anyone know where the CEM is? I'd like to pull it an check for water damage...

The problem might have started with water intrusion, but now it happens when it's hot, perhaps there is corrosion present.

I wonder if Volvo has a fix for the water intrusion problem detailed anywhere?

Steve

On our 2005 S80 it's located above the drivers feet. They say in some of those write-ups that at some point in the production run Volvo made some changes to the grommet and it seems they also refer to some sort of deflector or shroud change. Maybe you could get a look at a later model and see how it was handled.

Good luck.

If it was water or moisture intrusion, you have a good chance of corrosion build up which causes electrical resistance to increase. This alone will mess up signals going to all those wonderful computers etc. in these cars. Reminds me of the old days and bad battery cables. Starts perfectly cold, no start hot or warm. Operated on the cables and they were loaded with corrosion.

Believe you are on the right track!

dick