Hi all,

About the same time that my transmission started acting up, I began having electrical problems with my XC90. It started with radio/ICM intermittent behavior, and it progressed to a complete shut-down of the "low speed network". At this point, nothing inside the car works. You are in limp home mode, though the engine still works normally--no dashboard, no windows, no seats, no climate control, etc.

I read everything I could find on the internet (this forum and several others). I first investigated the CEM module for corrosion--had it big time. I removed the CEM, took it apart, and cleaned it with 99 percent alcohol and a toothbrush. When I put it back together, I had better behavior but not perfect. The low speed network would come up for about two minutes and then shut down again with messages about brake failure and airbags. The ICM was still dead, so I assumed there was still a problem there.

I disconnected the network connector on the back the ICM (green connector), and (big clue) the DIM (dashboard) came up and stayed up, but the driver's door didn't work. After studying the wiring diagram, I realized that disconnecting the ICM breaks the network ring. So, next I placed jumper wires on the back of the ICM connector (connect green to green and white to white).

Everything worked except, of course, the ICM. This gave me confidence that, if I replaced the ICM, I would be back in business. I bought one used (see another post), and all works now.

This was potentially a $3000 hit. Volvo wouldn't ante up. They did for the transmission, which was appreciated. This cost me a little under $300 and a fair amount of my time and effort, and I feel good about the result.

If anyone wants to pursue something like this and needs advice, let me know.

Dan

 

My first post about our 2005 Volvo XC90 with 146K miles. We have been having worsening issues with what seems to be transmission slippage... car almost feels like its intermittently slipping into neutral and out again over and over, usually when backing off gas pedal and pressing down again. We took it in for service, and they couldn't find anything wrong. Now, over Thanksgiving weekend, and 150 miles from home and ANY Volvo dealership, the car will not start. It will turn over, but doesn't seem to be getting fuel. Could these two issues be linked? Any input would be greatly appreciated!!! T

 

The transmission symptoms you describe are very similar to those I experienced resulting in a transmission replacement. I recommend you check with your dealership and Volvo directly to see if they are willing to cover part of it as they did for me.

Also, if it's a T6, it has an American made transmission that might be addressed for less money at a place that specializes in rebuilding them.

Not starting would be a separate issue, possibly a bad fuel pump.

Hope this helps.

Dan

 

Great post on the electrical problem with the XC90. Sounds like ours had the same problem today, I'm just going home to check it out. Can you tell me where the CEM is located? And is the ICM the "radio"? I've had it out due to intermitent operation but didn't find anything. I'll try the CEM cleaning, just need to know where to find it! Thanks. Bill

 

The CEM is located under the dashboard by the driver's left foot. The exposed part has fuses on the outside. Removing the CEM is a fair amount of work because you have to remove the windshield wipers and "cowl" to gain access to the top of the CEM so you can disconnect two cables on the top. There are a couple other tricks. I am working on a separate post to describe in detail how I did this.

If I were you, I would try to be sure that the CEM is the culprit before investing your time. Can you describe the symptoms your car is exhibiting? Be as specific as possible--sequence of events, associated lights/messages, etc.

Thanks,

Dan

 

Some more info on this subject:

The car has two main networks--the CAN network and the MOST network.

The CAN (Controller Area Network) is implemented by connecting all the modules with a twisted pair of wires, one green and one white. The CAN has two parts, the high speed and the low speed. In general terms, the high speed network controls the vital functions--engine, transmission, etc. The low speed network controls most of the things inside the car--dashboard, climate control, Infotainment Module, windows, seats, etc.

The MOST (Media Oriented Systems Transport) is implemented by plastic fiber optic cable. It is limited to the entertainment system. If you look at the connections to the ICM (Infotainment Control Module), you will see both CAN and MOST connections.

All my problems were associated with a communication failure on the low speed CAN network. One weakness of this system seems to be that any one of the modules can fail in such a way that the entire network shuts down (high or low speed sides, not both at once unless it's the CEM). In my case, the ICM was hogging the network and not allowing the other modules to communicate. By disconnecting it and jumpering the connector as I described, I was removing that distraction and demonstrating to myself that all was good elsewhere.

Another weakness of the design seems to be this: even a dealership with the so-called VIDA computer system can have a hard time diagnosing a failure of this type. Because the network is overloaded with bad data, the VIDA computer has a hard time querying each module to see if it is healthy.

In my case, the dealership told me I needed a new DIM (Driver's Information Module--basically the dashboard), but the DIM was and is fine and was shutting down with the rest of the low speed CAN network. I saw a post on another forum in which symptoms similar to mine were caused by the DDM (Driver's Door Module). The DDM is attached underneath the window switches on the door and is apparently susceptible to water damage.

So, how do you know where to start? This is what worked for me.

First, do a hard reset. Turn off the ignition and remove the key. Locate the battery under the floor near the tailgate. Remove the plastic cover. Disconnect the negative (black) battery cable. Short the negative cable to the positive cable. I held it there with one jumper cable clamp. WARNING, be careful not to short the battery terminals--the negative battery terminal should be sitting happily not connected to anything. Leave it this way for about 30 minutes. This procedure removes all residual power from all modules resulting in a reboot--a little like taking the battery out of your laptop.

Now, turn on the ignition and watch the behavior carefully. In the short time before everything shuts down, the working modules will be attempting to communicate. In my case, the DIM was working, seats and windows were working, but the ICM never came up. Eventually, everything ends up where it started (dead), but, in the interim, you might discover where the problem lies.

Final thought: as a trained but not practicing electrical engineer, it is incredible to me how this system is designed. The radio taking down the whole car--are they kidding me? The way it should work is that the central computer should have the ability to turn off an offending module, display a message to the driver, and keep everything else going. Actually, you don't need to be an engineer to realize this--just someone with a brain--frustrating as heck after paying $55,000.

Hope this helps someone.

Dan

 

Technically, the ICM is not the radio. It is the Infotainment Control Module. This consists of the small rectangular screen and the buttons to each side of it. Behind the screen is a small electronic module with CAN and MOST connections on the back.

If you decide to replace the ICM with a new unit from the dealer, you have two choices. You can get the whole ICM with the buttons for about $1000 or just the screen with the attached module for about $700. One complication is that a new one will not have the needed software loaded. You have to purchase the software separately and pay someone with the VIDA system to load the software.

I bought mine used from eBay seller volvopartsonly. He sent me the whole ICM (with buttons and software) for about $250. There is more than one ICM part number, so make sure you get the one you need. According to a Volvo mechanic, the ICM and its software is not keyed to an individual car like the CEM would be, so it's plug and play if you get the right part number.

Dan

 

Dan, thanks for all the good insight. I'm going to do the hard reset now and then see what happens. Here's the sequence of events, near as I can remember. The radio worked when the car was started from 10 seconds to 4 or 5 minutes, mostly about 20 seconds, then nothing. At night you could see the lights in the conslole fade in and out. Two days ago all the dash and the console lights all went dark all of a sudden and all the guages dropped to the zero pin. Car still runs and starts, the red alarm light on the dash flashes constantly running or not. When the engine is running the guages are all dead except the tach is trying to work (like it's vibrating) but it doesn't really move off the stop. I'll repost after the hard reset. The seat works. Bill

 

Went to do the hard reset, did as you suggested with the battery reset, started the car and waited for the antics to begin. So far....no antics. Off and on a couple of times and waiting for the failures to begin but nothing yet. I'll drive it and report back.

 

Drove around to see if anything would fail. The radio ran longer than ever but then faded to the right speakers only (typical just before it quits) and then quit. BUT, the dash and console operations are lighted and working. After errands the starter bobbled, acted like a solenoid, then started. It did this last week but I found the neg batt cable loose and tightened it. Starter seemed better but now I'm not sure. With so many electronic things to go wrong I'm not sure if it is a simple solenoid or starter problem or an extension of all the computer issues. I think Subaru B9 Tribeca is sounding pretty good at the moment!

 

I would try disconnecting the CAN connector from the back of the ICM and jumpering white to white and green to green on the back of the connector. This is relatively easy compared to investigating the CEM. Drive with it for a while and see if everything else stays up. If it does, you then know you need an ICM.

If you need the procedure for getting to the back of the ICM, let me know. Good luck.

Dan

 

If you decide to trade the car, be ready for a big shock when you see what they are willing to give you in trade. I was going to trade it for a new Volvo XC60 at a point when the DIM was dead. The Volvo dealership offered me $4000 in trade for my 2005 XC90 T6 with 91,000 miles. One of the reasons was that the car would have to be sold "mileage unknown" due to the fact that, without the DIM, you can't see the mileage.

I ended up buying the XC60 anyway, kept the XC90, and fixed it myself.

Dan

 

Hi Dan,

I read your tread and you mentioned that you removed and cleaned CEM on your XC90. I believe I have the problem with cem and would like to clean it before going to dealers for spending $$. My radio works perfect, cd doesnt read anything, and I lost the power in car (all gauges, windows, radio). Before it would shut off there was a clicking sound from under the steering wheel, where cem is located. If you can give me instructions on how to remove it that would be great. Also how can I check if my car has faulty planum that leaks water on CEM, or if it was replaced? Also what I noticed is that there was a hole in the carpet on the drivers side and that foam underneath it was moist. Maybe that is where my wires are shorting, but I might be wrong.

I have 2004 XC90 2.5, 128000.

Thank you,

Marko

 

Hi Marko,

As I mentioned earlier in this post, I would recommend trying to make sure that the CEM is the culprit before removing it and trying to clean it. It's been a little while since I did this, but I'll try to walk you through it to the best of my memory.

Disconnect one of the battery cables.

Remove the windshield wipers. After you remove the nuts, the wipers probably will not be free. The trick is to tap on the arm a couple of inches from the nut in the direction of the blade. Use a plastic mallet or a piece of hard plastic between the hammer and the arm. Use a bunch of light taps. If you hit it too hard you will break the arm. Also, it's a good idea to mark the position of each arm to facilitate getting them in the right spline on reassembly. Also, driver's and passenger's side arms are not interchangeable. I left the wiper blades on as the unprotected arms can crack the windshield.

Next remove the cowl--plastic piece that runs along the bottom of the windshield. You may lose or break the fasteners, but they are cheap and available from the dealer. Note how the upper lip of the cowl engages the windshield glass to facilitate reassembly.

On the driver's side beneath the cowl you will see a rectangular cover held on with clips. Before you remove it, check to see if it is seated properly. The housing that the cover mates to is the plenum. It is bolted to the car. My bolts were loose, and I believe water was getting in between the housing and the metal structure.

If you have the modified/updated plenum, it is all one piece, and I'm not sure how you would remove it. But, if it's leaking, you probably have the old style one. I think these are ok if they are assembled correctly, everything is tight, and the rubber gasket is in good shape. When I put mine back together, I used some silicone grease (not adhesive) to help the gasket make a good seal.

Once you have removed the cover, you will see the top of the CEM. You have to release the two connectors on top by moving plastic levers to the release position. Also, there are two torx screws on the top of the CEM holding it to the bracket. They are hard to get to but must be removed.

The rest is done from inside the car.

There is a spring loaded bracket on the side of the CEM. When you push it out away from the CEM, you will be able to rotate the CEM away from the bracket. You have to remove several additional connectors. Then you can remove the CEM and bring it in the house.

The CEM housing consists of two L shaped halves. They can be separated by gently prying the snaps back with screw drivers. You will now have access to the boards. If yours is like mine was, your top board will show evidence of corrosion around the IC pins and the connectors. For some reason, the top board (the one most susceptible to corrosion) is the one that's not coated!

I cleaned mine with 99 percent isopropyl alcohol and a toothbrush. I had to order the alcohol from my pharmacy as what they had on their shelves has too much water in it. I thought of this idea because it's the same process used to remove excess rosin from PCB's after soldering. The alcohol should not damage the components, and it dries quickly. It goes without saying you need to be careful with the fumes--they should not be inhaled and are flammable. Also, wear eye protection.

You want to wash and scrub with the toothbrush to remove as much of the loose corrosion and mold as possible, especially where it is bridging the pins of the IC's or connectors.

Before putting the CEM back in the car, I would suggest tightening the plenum bolts, making sure the rubber around the cable harness is seated properly, reinstalling the cover, and using a moderate spray from a hose to make sure it's not leaking. This is best done as a two-person job--one directing the water and one with a strong light inside the car looking for leaks.

That's about it. Reassemble, reconnect the battery, and hope it works. As I understand it, CEM's are not interchangeable without reprogramming, so it would be great if you could get your original CEM working again.

Best of luck, and let me know how it goes.

Dan

 

Hello Dan,

Thank you for the info. I was able to remove CEM and here are some of my findings. That whole area and CEM itself are dry as desert. My car is actually 2003 so the cem is not and L shape as yours but its a rectangle that is fitted to stand upright. It can easily be removed from inside without even removing vipers and cowl. CEM was dry no corrosion and its whole protected with(I am guessing here) orange colored anti moisture film. I put a hose and let the water run inside the cowl area and there was nothing leaking in the driver side. I went to the passenger side(as the carpet underneath was moist on both sides(previous owner said he had that problem cleaned sunroof drains and it was gone) and took out the YAW sensor which was corroded like it was sitting on the bottom of the ocean for years. I opened it up sprayed it with anti corrosion/moisture displacement spray) have to say it looked like brand new and put it back. I been driving since with no loss of power but I still had anti skid/srs message on. Went to my mechanic who was able to remove srs code with vida but could not remove anti skid. First there was no communication with steering angle senor then there was BCM accelerator malfunction code. After that I had a low battery message and he could not try anymore. I will go tommorow to see him and see if he can remove code. Car runs ok so far.

Any thoughts on these codes/situation?

Thank you

 

No, I'm afraid your issues are different than the ones I encountered. Good luck.

Dan

 

Hi Dan:

I have read several of your posts and you sound very knowledgeable about the XC90 electrical problems. My wifes 2005 XC90 has had radio problems for the past 6 months and it finally has gone dead. It plays for approx. 5 - 10 seconds after you start the car and then goes out. The backup alarm doesn't work anymore either. Do you think it's safe to say that the ICM has gone bad?

Thanks,

Brian

 

Hi Brian,

I think it's a likely candidate. The seller on eBay that I mentioned in another post was very helpful. He might be willing to sell you one with return rights if it doesn't fix the problem. Make sure you get the correct ICM--there are at least two different ones depending on the options you have.

By the way, my car has been running flawlessly since I made the repair to the CEM, changed the ICM, and got Volvo to replace the transmission.

Let me know if you need any more advice (the free kind, for what it's worth).

Best,

Dan

 

Thanks Dan. I will let you know if it fixes the problem.

Brian

 

hello, I came across this forum in my search for possible causes of a problem I encountered while on a road trip.

the vehicle is a 2005 XC90 V8 built Oct 2004. It has 128K miles on it, always dealer serviced and maintained. It has pretty much every option that was offered.

before this road trip, we would occasionally see an issue with the turn signals. they would not always work when requested. we have also had issues with the right side front door speaker cutting out.

On this trip, we were on I70 heading towards Vail. Traffic was heavy and there was a lot of sitting on the road. things finally picked up and we were able to run normal speed up to the Eisenhower tunnel. About 1/4 mile into the tunnel, the engine started cutting out. I backed off the throttle and it jerked back on, but quickly cut out again. It cycled like this the rest of the way through. speed dropped to about 35 mph and that's all we could maintain because the engine cut out for a few seconds, then power back on suddenly, and then cut out again. there were no warning lights, messages, or any other strange behavior. the speedo and tach worked the whole time as well.

I made it out of the tunnel and pulled over. I let the motor idle for a moment and then shut down for a few moments. When I restarted, the indicators went nuts for a second or two, and then started working normally. We were able to roll the rest of the way to Dillon to our stop for the night.

the car has been since.

Could this be indicative of a pending CEM failure?