tpaxadpom

I have 550i 2009 with non working alarm. I can talk to the module, it senses when I jack the car and lights begin to flash, but the siren is dead. I have M aero package. Where is the siren supposed to be located? Looking at TIS I see it is on the passenger side inside the rear bumper, but I have M sport bumper and I don't recall seeing it there when I remove it on my 550i 2010 though I could be wrong.

dingolfing

The siren is indeed behind the passenger rear tire. When you remove the bumper, there is a large black plastic bumper mounting bracket (with large circular holes) that also secures the wheel well liner. The siren is mounted on the inner side of this black mounting bracket, and you can't see it until you remove the bracket from the car body.

If you aren't the original owner of the car, don't be surprised if you find the siren missing or disconnected. Once the car alarm sets a hard fault, the siren never turns off, even after resetting the alarm. The only way to reset the siren is to completely replace the module. Since no one wants to replace that expensive item (on an older car), the easy solution is just to disconnect the siren.

tpaxadpom

Thank you dingolfing. I will try to get to it in the near future.
It appears that the backup batteries inside the siren can be easily replaced. I already have a replacement siren ready to install just didn't want to remove the bumper for no reason. Though I will get new batteries just in case. See here.