Front Axle Levels Sensors
For the front sensor, it should be connected to the RHS control arm and located at the non-moving end with its position sensor arm able to move freely. This end is attached to the swing arm I think. If you have air suspension all round, it's all part of the same sensor system, but with the additional functionality built in.

Rear Axle Level Sensors
Hall effect sensors are mounted on the left and right sides of the rear suspension for ride height detection. They are pivoted by a
coupling rod through the rear axle swing arms.
The hall sensors produce a varying voltage input to the control module as the suspension height changes.
If the vehicle is equipped with Xenon headlights the right side sensor contains an additional sensor for the automatic headlight
level adjustment system.

In both cases look for a block (the sensor) and it's associated levers on the RHS control arms at both ends of the vehicle. You may have sensors in all corners if you have full air suspension, but only the two on the RHS are used for the light levelling system.

I do have a copy of a BMW TI (in pdf) of how to install the Xenon HIDs as a retrofit, but can't upload it as it's too big (1.2MB). It has all the diagrams of where the sensors are and the wiring etc. Only for use on LHD cars!!

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