E60/E63 Alarm Siren error

So for the past 2-3 months I've had a fault code pop up on the 630i under the DWA (alarm) module. The code indicates that the internal batteries inside the siren are expired. BMW throw away the siren in this case as that's what it says to do in DIS and ISID.
The unit is over €200 new but all that is wrong is the batteries in side are gone. They are camera batteries, CR17335 3V to be specific. About €4 each, you need 2. Big price difference compared to a new unit!

The batteries are there so that the alarm can still sound if a car thief disconnects the car battery. The siren is located behind the rear bumper on the right hand side of the car. Same general area for both 5 and 6 Series. Probably the same for the e90 3 Series too.

So I got to work removing the bumper, I only needed to partially remove the bumper to expose the bumper carrier. The siren is located behind the carrier.

http://i175.photobucket.com/albums/w...psip9wadg0.jpg

http://i175.photobucket.com/albums/w...psnrw6drm2.jpg

http://i175.photobucket.com/albums/w...psjqvgna2x.jpg

The BMW siren is actually a Gemel unit:

http://i175.photobucket.com/albums/w...pshtiqcsjx.jpg

http://i175.photobucket.com/albums/w...ps0gfzlmoz.jpg

http://i175.photobucket.com/albums/w...psdyczkgkl.jpg

http://i175.photobucket.com/albums/w...psqbv6ct1g.jpg

http://i175.photobucket.com/albums/w...pskweb18h3.jpg

It was an easy enough job to undertake and I just finished in time for the 24hr rain deluge that is underway right now!

Anyway I cleared the error and it has not come back! Result!

E60/E63 Alarm Siren error - 9D12