As the body controller is based on the BMW GM5 unit and the E46's did have this option, i picked one up from a scrappy, p/n 8 386 932 there are plenty on ebay ranging from Â£2 upwards, if you want to have a look click the link http://www.ebay.co.uk/sch/i.html?trksid ... &_from=R40
There are only 3 connections to be made, pin 1 goes to the BCU (Body Control Unit), pin 2 to 0v and pin 3 to an alarm active switched +12v.
Pin 32 on the bcu plug (C0660) is not populated and you will have to add a connector with a length of wire to go to Pin 1 of the tilt sensor module.
The switched +12v required is taken from pin 15 of the bcu and is a yellow/pink wire, make sure you identify the correct one as there are 2 on the plug, the other is permanent +12v for the RF receiver.
0v can be connected to a black wire or a chassis bolt.
The unit needs to mounted flat and on the E46 it is mounted at the rear on the offside, i mounted mine close to the bcu.
Once the car is alarmed the tilt sensor records its current position and any deviation on the X / Y axis will trigger the alarm, a quick check on the T4 (Testbook version 4.Computer Diagnostic System) showed that the alarm trigger was due to the "tilt sensor"
So our cars are all set up for this additional module but was never fitted
Usual disclaimer, you do this at your own risk!