2003 S80 Siren module completely missing/removed.

[juris]

Good evening guys, a new poster, but I hope that somebody on this forum could help me out. This is an xpost from another forum as I am trying to cover as much ground as I can.

I bought a 2003 2.4D automatic S80 in Belgium a couple of months ago knowing that there were some issues with the car, but, hey, it was cheap.

Initially I noticed that the remote fob was not working (i did not notice the dome lights and the mirror as I was not aware of these issues being connected at the time) and the car had to be unlocked with the key as well as the battery was completely flat so the car had to be jump started. After arriving home, I noticed that the sunroof, dome lights, self dimming mirror with the seat belt messages did not work as well apart from the remote locking with the key fob.

Long story short, I changed the batteries in the fobs and it still did not work, so I started googling and as you all know - the internet is just exploding with information regarding the dreaded siren module failure. So it took me some time to source a replacement module as well as I had to battle a few other issues along the way (repairing windshield washers that cut out on me, which resulted in repairing the CEM as it had broken pins due to a leak).

I hooked the car up to VIDA/DICE and it showed that the UEM has no power to it. As I read that the siren module can overload the LIN line and this can affect the operation of the UEM, I did not make much out of the message and braced myself to replace the siren module. There were no messages in the DIM regarding the alarm service as well as there aren't any currently, hence I haven't dug any further regarding this.

***Sourced the replacement part, got the rivets and a drill etc. Removed the arch liner and to my surprise - there was no siren module present there. At all. The connector was neatly fixed in place, but that was it. The bracket that holds the siren module wasn't there either.

Suffice to say that I plugged in the replacement module without any luck. No results.

As much as I can deduct, somebody with knowledge must have done this on purpose, but now I have a bigger challenge on my hands - I need to find out where the electrical connection to the UEM might have been cut/broken. The fuses are intact, those were my first stop to check. The plug in the driver's side pillar is connected as well.

Does anybody have any suggestions which way I should start digging from? I do not even know what to do, but I know that I will not take it to a volvo tech as it will cost me way over the value of the car.

Should I even attempt to repair something like this (thinking of issues that might arise, if repaired)? Does anybody have any clue why somebody would do something like that?

Regards and thanks in advance,
Juris.

[draser]

I'd get an wiring diagram and find the UEM circuit and go from there.

[Florida Wheel]

I have pulled the siren fuses, then reinstalled them to reset the circuit. I've heard that you can also remove the negative cable from the battery, wait ten minutes, then touch the negative to the positive terminal. This resets the circuit. Then reinstall the negative side and you should be good.