UEM swap out

deano1 · Post by **deano1** » 31 Jul 2023, 17:15

Just wondering if the UEM module is part number interchangeable?
Reason why is CEM is shutting down entire vehicle after about 5 minutes after you turn off ignition. Now the car completely shuts down after being turned off for 5-10 minutes and I lose the key fob fucntions/interior greeting lights?
But turn the ignition key to position 2 then back to position 1 then again to position 2 and everything powers up and all functions are active once again including fobs.
I have another UEM with same part number but I don't know if I can just plug in another UEM with fob frequency to deal with? Maybe worth a try but just worried I'll make things worse.
This all started after I sent CEM out for rebuild at Xemodex.
Been working with Xemodex customer service and doing a lot of searching of the webs but I'm still at a loss for why this situation persists when all was fine before the CEM transfer?
Cheers

yanga001 · Post by **yanga001** » 31 Jul 2023, 18:17

What kind of codes are you pulling? I sent you a private message.

The upper electronic module (UEM) manages not too much as far as i know. The alarm system is managed by it I believe along with the rain sensing equipment in later models.

deano1 · Post by **deano1** » 01 Aug 2023, 04:37

I ran codes in VIDA last night and all came up clean. But I swear I was getting "UEM not communicating" or "UEM offline".
I've done UEM resetting procedure so what gives?
Did a little digging around and it seems Volvo had at least 2 frequency UEM 315MHz and 433MHz. for the fobs.
By part number mine should be the 315MHz. as well as my scrapyard find as they share part numbers.
"Anti Dazzlers" is Swedish for rear view mirror. Oh those crazy Swedes!
I maybe able to just swap it in?
Cheers

Post by **scot850** » 01 Aug 2023, 17:17

Is it a case of it works or it doesn't?

Neil.

yanga001 · Post by **yanga001** » 01 Aug 2023, 18:22

I would not think it would make things worse as these cars are not known to lockdown on a module swap. They may complain but it should not immobilize the vehicle. I would keep the doors open, disconnect battery, do the swap, reconnect battery, and see if the system works. Also check if you can save configurations of the UEM if possible. if you can then you may be able to load it onto the other module. Ill check when i get back to the house today.

deano1 · Post by **deano1** » 02 Aug 2023, 04:12

I just wanted to check here to see if swapping UEM could trigger immobilizer to erase key or erase Fob for good but it seems general consensus doesn't thinks so.
But when I really think about it, the key FOB does work, but only within the 5-10 minutes after car is shut off. So that system does work.
So it's my belief that CEM is timing out or something?
Maybe it's not happy about a module configuration?
But whatever it is it seems to be causing CEM to completely shut down and the only way to wake it up is by applying power thru key on situation.
Trust me I've read just about every thread and topic on here and never seen this type of situation come up.
I almost got thru the "CEM swapping" thread but then realized that although I'm interested in the CEM's multiple functions, I'm just not equipped or able to do that stuff, but certainly interesting watching these guys dissect and reverse engineer out in the wild like that.
cheers

Post by **vtl** » 04 Aug 2023, 09:33

I found my 05 XC70 is locked yesterday (I never lock anything) and the fob does not work. Had to open it with they physical key, only then the fob was brought back to life. Something is off. It's been hot and humid around here for a few weeks.

Post by **jonesg** » 04 Aug 2023, 12:15

vtl wrote: ↑04 Aug 2023, 09:33 I found my 05 XC70 is locked yesterday (I never lock anything) and the fob does not work. Had to open it with they physical key, only then the fob was brought back to life. Something is off. It's been hot and humid around here for a few weeks.

happened to me, even with keys in the ignition.
Had to leave the window open when working on the car to prevent lockout.
i think it was either the fob battery or dribbling nicad acid on the alarm module board.
I addressed both and the problem went away.

deano1 · Post by **deano1** » 05 Aug 2023, 15:57

In my situation my alarm module functions fine.
Mostly I'm thinking I have a CEM problem because whole car shuts down about 5-10 minutes after key in position 0 and no way to wake it up with fobs. Only way is key to position 2 then position 1 then on second attempt position 2 everything lights up starts and runs fine!
I had CEM code 1D08 when I ran VIDA so I believe that's the problem.
Just waiting for Joshua at Xemodex, he's on Vacation now. Once he gets back we'll continue our investigation.
Cheers!

Post by **precopster** » 05 Aug 2023, 16:31

In my experience and after having many discussions with Henry (known as Doublebug here) you can swap out a UEM with any other of similar year as long as the matching key fob is used.

The issue is the key transponder (small glass tube) which is housed within the key fob will need to be swapped over to the new key fob so the vehicle will start and of course you need the original key blade too. Swapping the transponder and key blade is easy because it is housed in the separate key blade head which separates with just one screw.

There's quite a few posts here about doing this.