Alright, I just bought this '04 S80 two weeks ago. Great condition and I couldn't be happier. I noticed that when I lock the doors with the remote, the turn signals would come on for a second or two and then shut off giving a visual confirmation that the alarm had been armed. Then all of a sudden last night as I got out of my car, it no longer does. The alarm warning light still flashes on the dash, when the doors are locked but the lights do not flash.

Any thoughts as to what would cause this change? It worked yesterday afternoon!
Thanks!

EDIT: SOLVED! After a couple hours of searching and combing the net I found the reason. I had checked all the doors/trunk to make sure they were shut properly but not the hood. When I filled up with gas last night I checked the oil and didn't close the hood hard enough so that it triggered the alarm to know it was good to "secure" the vehicle.

Hopefully this post will serve someone else in the future

 

My 2003 does that on occasion too. I just figured it was because of the near-dead rechargeable battery in the siren module. Unfortunately they put it in a wheel well and you have to drill out rivets to access it.

My Volvo trouble code reader shows UEM-0004 by the way.