Urgent Help Needed: 2004 V70 2.5T Limp Mode on Road Trip. [CEM overheat ] Topic is solved

rntaboy · Post by **rntaboy** » 27 Jul 2022, 21:54

I'm on a cross country (2500 mile) road trip after buying a nice looking 2004 V70 2.5T.

Everything was going smoothly for the first 250 miles, but then the car started making a clunk noise (just one clunk sound per incident), followed by the aftermarket head unit flickering. This happened a few times, and then the dash started giving brake/ABS errors, then the dash cluster died and the car went into limp mode.

Shutting the engine off and starting it back up everything will work for a brief period before the same issue occurs. With my limited experience this seems like a CEM overheating issue. I'm going to try to take it to a Volvo shop ASAP tomorrow to see if the can figure out the cause, but I've heard sometimes it's difficult for a shop to replicate the issue.

First off, does anyone have any experience with these symptoms?

If it is a CEM thing, does anyone have any experience with a CEM overheating, and possibly anything I might be able to do to keep it drivable for the remainder of my trip?

Would blasting the AC as my feet help, since that's around where the CEM is located?

If the CEM does overheat, is there anything I can do to quickly cool it down?

Or how long would it take the CEM to cool back to a normal temp if I gave it a break?

Would driving a night help, since it will be cooler outside at those times? I'm just throwing whatever at the wall in hopes something might help.

Considering a CEM replacement would probably leave me stranded for a number of days, I just really want to avoid being stuck 2000 miles from home with a broken down car.

Any and all help would be much appreciated, as I am clearly desperate right now.

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Post by **br0dy519** » 28 Jul 2022, 03:03

Your CEM diagnosis may or may not be correct. Hard to tell 100% without using VIDA to read all of the car’s codes. Yes running the AC helps. Some people have added a 12v computer fan to blow on the CEM. I would probably just unclip it and hang it near the air vent and take frequent breaks if I were on the road.

If you’re with the mrs. and she brought a hairdryer or if you’re at a hotel with a hairdryer, try the CEM heat stress test here : https://xemodex.com/us/pdf/DIM%20CEM%20 ... eMODeX.pdf

You were sent this link in your other thread before. Did you ever figure out your low voltage issue? It sounds like a related problem …

rntaboy · Post by **rntaboy** » 28 Jul 2022, 06:38

Thank you for the response. This 2004 V70 2.5T is actually a different one from the V70 I posted about previously. I didn't end up buying the previous one due to the CEM issue and the seller being a nightmare. The V70 I did buy seemed like it was in much better condition, and nothing popped on the inspection I paid for.
Imagine my surprise when basically the same symptoms popped up on the one I purchased after I'd driven 220+ miles east through California.

Post by **vtl** » 28 Jul 2022, 08:21

I've had all sorts of weird issues with the car when my DIY CAN project disturbed the CAN bus. You mentioned aftermarket HU. Is it connected to the CAN? Any third-party steering wheel controls adapter? Try to disconnect it and see how it goes. It may sit behind the HU, your car has a CAN-LS lines behind the HU, which is sufficient for SWC adapter.

Post by **vtl** » 28 Jul 2022, 08:23

Also, is it AWD car? If yes, DEM (Haldex computer) can do that as well. DEM is connected to BCM. It is poorly insulated and is placed in a worst possible place. Try to pull the DEM fuse or, better, the DEM connector. I've had a rusted out resistor in DEM, it was causing signal reflections on the CAN bus, pulling the fuse alone didn't help.

motormikeyman · Post by **motormikeyman** » 28 Jul 2022, 08:48

Ditto to all of those issues when I bought my '04 XC70. Drove me nuts until I discovered that cleaning the main CEM connector cured all of those woes for a while (usually about a year). The last cleaning did not work however. I finally wound up backing the connector out 1/8" and have not had an issue since. Those tiny pins are sensitive! Not saying this is your issue, but it's easy enough to eliminate

rntaboy · Post by **rntaboy** » 01 Aug 2022, 13:35

As an update for anyone who cares, I was able to drive the car without issue the remainder of the way by removing the cover and using a 12v fan to cool the CEM. It was displaying the clicking sound Xemodex mentions on their diagnostic flowchart, so I'll be sending the CEM off to them for a remanufactured unit.

Post by **abscate** » 02 Aug 2022, 03:08

Nicely done , and glad you are safely back in Ohio! Looks like the CEM overheat was root cause!

deano1 · Post by **deano1** » 02 Aug 2022, 04:21

I think that my 2002 base s60 is also experiencing the dreaded CEM failure.
Starts fine when cold but fails to start after running for a spell because fuel pump is not activated after it gets hot.... Yes, I replaced the pump and same symtoms

So while doing some sniffing around the Xemodex site the dude in the demonstrating the CEM removal in the video mentions a product they use at Xemodex called "Stabilant 22", it's a Contact enhancer.
Read about it here https://www.stabilant.com/Appnote1.pdf
Then check it out on the YouTube, very interesting product.
I placed my order as to power up my electronics tool box.

Post by **br0dy519** » 02 Aug 2022, 07:38

https://shop.wurth.ca/electrical/electr ... L/893.622/

Looks expensive. I'm not sure where they would use this? It's not the same as adding dielectric grease or anything. It looks like it's actually conductive. Anyways, be careful. I know part of their CEM repair process is adding a massive heatsink onto the PCB, and coating the PCB in a waterproofing "dip" looking thing, which helps with those pesky 2004 water ingress issues.