About a year ago our 2004 xc90 would not start occasionally. The battery is new. An AAA technician showed me how to disconnect the battery for a few minutes, then reconnect and the car starts every time. The dealer has not found the problem because it is never happening when I take it in. Recently while driving I have lost all power to inside the car, lights fail and steering becomes stiff. This has happened twice so far. Once I turn the car off and back on it starts and runs normally. Neither of these problems seem to have any
basis on driving conditions, weather or how long the car has been drive at the time..
Could these 2 problems be related? We did have the drain problem a few years ago and the dealer fixed at no charge.

The car now has 120,000 miles and new transmission about 5000 miles ago

 

when you have the problem again, try to turn on the interior lights. if they don't work, it suggests the battery cables are loose or corroded, either where they connect to the battery or where the negative is grounded to the chassis. ignition switch is another possibility. what exactly does it do when it doesn't start?

 

I can tell you from experience that it is the CEM!! Total electrical failure while driving on interstate at night, engine maintained running though, but the failure would continue to due so sporadically. The weird thing was this all started to happen after opening the sun roof, (as we had not had the car but a couple of months, and it was the first time to open it), may or may not have had anything to do with the drains. Then, one day a couple of weeks later while shopping, the car just would not start. had it towed home, because wanted to do some research before taking it to Volvo. I pretty much found, while digging around on this forum, the identical symptoms that others had experienced. I then went to Volvo, (and much to my surprise, the adviser there looked puzzled, and claimed he had never heard of that...B/S I thought to myself) he then told me to expect 4 - 5 hours labor to diagnose (as im calculating in my head @$100/hr). I pretty much knew right there I wouldn't be taking my vehicle to them. I called a local shop that had a Volvo specialist and questioned them, $99 diagnose fee. Their findings came back just as my research led me to believe, and their repair/fix was in the same ballpark as what I gathered from others on here. At least I knew, as it wasn't really a shock when they told me the price, but still it was a lot! I would certainly do some research on your year and model along with CEM and see if it coincides with what is happening with your vehicle.

Additionally: The wipers would activate when the power failure occurred, each time the failure occurred, it was instant, come right back on.

I read somewhere after our vehicle wouldn't start, to disconnect the neg battery terminal for about 20 -30 minutes, then reconnect. After doing so the car started, allowing me to drive it to the mechanics.

If you decide not to take it to Volvo, I may suggest looking for a shop in your area that deals with Bosch Service, they gave me a line of credit towards the repair with 6 mos no interest.

Our repair cost was just over $1700, but they had to replace 16 relays due to corrosion - they also asked me about the windshield being replaced, I informed them if it was, it was by the previous owners. They concluded that water was leaking at some point thru the windshield, into the relay box, and into the computer located by the drivers foot kick panel. Another cool thing about the shop we chose, when I picked up the car, they gave me the CEM and relays they replaced!

Hope this helps!

 

Divincem- that is the CEM, not the ECM.

 

I stand corrected......all the while still paying off that repair bill...lol!

Thanks

 

Haha no problem. Just didn't want someone to go get the ECM replaced and be put that money (it is also expensive)

 

I have posted a couple of pictures in "Photos" of the unit they replaced.

 

Yep your problems are identical to mine. I am wondering about the windshield leak also as the head liner and side panels are getting a bit loose in the front. Seems fine everywhere else in the car so I am thinking it is moisture. Also I have had a hard time clearing the window of condensation and fog the last 9-10 months, which is suspicious.

 

I have the same issues with the headliner and starting to separate from the windshield posts (slightly). I've seen and read some remedies online in here and other locations how to fix/repair that, but I'm just not one to have the patience to undertake such....i'll probably resort to taking it somewhere.

 

Mine started getting wet around headliner and posts but I found the drain tubes from sun roof to the outside stopped up. Just removed c pillar covers then drain hoses and cleaned them now all is fine. Found a video on youtube if anyone needs help.

 

Had exact same erratic problems, pulled out CEM and sure enough, water damage, white corrosion was dead give away. Found that the sun roof drains were clogged, repaired, also the drains in windshield wiper cowl were clogged, so in heavy rain, water would build up and leak into CEM compartment for rubber boot for wire harness was no longer sealed, rubber gets old and stiff, so pulled and resealed with rubber sealant, also do the same on top cover which also allows water into CEM compartment. I cleaned and brushed all corrosion on connector and around several components on top board which is crazy as it is not dip coated like the vertical board is??? It would make more sense to have both PC boards dip coated to protect from water corrosion given water just puddles on top of this CEM board. Used electronic circuit spray to insure all corrosion is removed, used a pipe cleaner to get into tight areas as well as tooth brush to remove the most stubborn corrosion on connector pins. In the end, it solved all my electrical ghost and intermittent failures of stalling, no power, cutting out, dash indicators blinking on and off, wouldn't start, you name it, every symptom in the book, so if you have these issues, start with CEM as I went through a fortune replacing fuel pump twice, fuel pressure regulator, fuel filter twice, cleaned out fuel tank, fuel pump relays, loose wires, usual tune up, so beware, this is a common problem, and in most cases, removing corrosion is answer, don't fall for dealer wanting to replace CEM for a fortune.

 

Had same exact erratic problem. Same issue with headliner against windshield, same everything. This form just saved me time money and the stress of not knowing what it was. To anyone who has this issue undo batter for a few min and it will start up to get you home. Got a deal on this vehicle knowing it wasnt major just couldn't track it down. Salute