I have a 2006 3.0i and I've also had the seatmat problem. Sometime it worked, sometime it did not recognize a adult person...so I decided to get rid of the seatmat. Replacing it at the dealer would have costed around 1000$...that's not a option in my eye.

The 2006 X5 would have been covered by a recall in USA..but as I'm living in Italy, no coverage at all.

The latest X5 E53 models (2005-2006) and respective seatmats, don't use a simple signal that you can reproduce with some resistors. It's a digital signal you have to reproduce with the help of a microprocessor.

I've found digital seatmat emulators on the bay...and used one for about 1 year. It did the job...but actually it caused other problems like sometimes the remote key not beeing able to lock the car or "key in ignition" ringing even if the key was not in the ignition. As soon as i disconnected the emulator..."key in ignition" message disappeared. Found the culprit!

I then bought another module, hoping that maybe this would behave differently. Installed it, no more strange behaviours...but unfortunately it drained the battery over night.

It seems that even if those emulators are able to get rid of the seatmat, they are not comunicating with the other modules as it should...

I ended up coding the occupancy sensor out with the help of BMW SCANNER...by unchecking "Occupancy classification System" and "Seat Occupancy Recognition" in the Airbag module.

It did the trick, but actually now also the seatbelt warning is not working, even if I did non disable it in BMW Scanner. I guess The Occupancy Classification System is needed for the seatbelt warnings to be active.... but it's just a guess.

I hope to be able to read the Airbag module with NCS EXPERT in future, to see what unchecking of the "Occupancy classification system" and "Seat Occupancy Recognition" actually did on the coding of the car... but at the moment I am not familiar with it.