Electrics: Is the CEM on my XC90 dying/dead?

[Parknest]

I've spoken to the specialist today and he told me that the CEM has come back to life. He's going to speak to his tech guy either tomorrow or Friday (27th/28th October 2022 for those who are reading this in the future). He's loath to send it off for bench testing as it would probably pass such a test as my problem happens more than 2 hours into a long journey and they don't do tests of that length. He said that the CEM might have to be replaced. At least he knows that there has been a problem when he collected the vehicle.

[Clan]

Originally Posted by Parknest

I've spoken to the specialist today and he told me that the CEM has come back to life. He's going to speak to his tech guy either tomorrow or Friday (27th/28th October 2022 for those who are reading this in the future). He's loath to send it off for bench testing as it would probably pass such a test as my problem happens more than 2 hours into a long journey and they don't do tests of that length. He said that the CEM might have to be replaced. At least he knows that there has been a problem when he collected the vehicle.

he needs to heat it up with a hairdryer for a while and look for cracked soldered joints

[Parknest]

I've just spoken to the specialist and he seems to think that my non-working DEM could be the cause of the dying CEM and he wanted to test it with the DEM unplugged to prove the theory. When I told him that the problem started after 2 & a half hours of driving he said that it was probably the CEM. As I'd like to have the AWD working in time for winter and the next caravan outing, the plan is for them to remove the DEM and then I'll arrange to have it repaired by Volvo Diagnostic. As soon as I mentioned Lukasz, my specialist knew who he was and had dealt within him a couple of times in the past without any problems. The specialist normally obtains secondhand modules and reprograms them but he says that used DEMs are hard to find (I managed to find a couple of used ones on eBay) so he said getting it repaired was the best option and he'd rather have me do the legwork myself which isn't a problem.

[Simmy]

try revtronics in bradford they repair all car electronic units cem / dem / dim . ect

[Parknest]

Simmy, I saw your post on my other thread and the response is there.

I'm going to get the DEM repaired by Lukasz at Volvo Diagnostic and I mentioned the CEM problem to him. He agreed that the faulty DEM could well be responsible for the CEM throwing a wobbly so the DEM is definitely going to get repaired/replaced.

[Simmy]

it was worth an ask at revtronics they have done dim repairs while you wait. if lucaz cant fixit no one can good luck with your repair keep us posted

[Parknest]

The DEM has already been sent off to Lukasz. He advised me to send it by Royal Mail Special Delivery which is what I did. Once the DEM has been repaired/replaced I can take it back to the specialist (Volvo Specialist Car Sales in Brighouse, West Yorkshire). They told me that it has been driving fine with the DEM disconnected but that's not a guarantee that the problem is solved.

[Parknest]

I ended up getting a reconditioned DEM as mine was beyond repair and I've taken it back to the specialist to be fitted.

[Parknest]

Sorry for the belated update.

I got the XC90 back 8 days ago and it is working fine. I've not done any long journeys yet which will be the real test. For now, I've got a fully working AWD with the dreaded "anti-skid service required" message finally banished. If the problem comes up again, I'll be straight on to the specialist for further diagnosis on the CEM. If it needs repair, I'll be giving Lukasz my business again.

[Parknest]

Just to add to this, I've only just pulled the dashcam footage (thank feck for 256GB SD cards) and the day that this happened (15th October 2022) I'd left home at 12.57 and the first sign of trouble happened at 15.42 (according to the timestamp) so I'd been on the road for 2 hours and 45 minutes. There was a thump from the transmission. About 8 minutes later there was another such thump and I started losing most of the electrics starting with the radio/CD player, what sounded like relays clicking from the general area of the CEM, the 2 messages on the display before the instrument cluster stopped working. The climate control and the headlights were working and I had limited used of the wipers. The engine was still running but the transmission appeared to be in limp mode. The fault codes at the beginning of this thread were the ones that came up when did a scan as soon as I got home.

I know this is long after the event but I'm hoping this information might be of use in determining if the CEM is actually at fault now that I've got a timescale of when this problem happened.