Deliberately designed that way by BMW!
All modules are serialized and won't communicate unless they are all in sync, you change or add the Alarm or Alarm and TPS module (note 2 part numbers) = it won't work, you change the ABS pump = and it won't work, and the same for the instrument display. All of these have to be programmed in by BMW themselves, no idea if you can approach them to ask to flash the unit to accept it on a second-hand part. There is a workaround, that involves desoldering electronics and re-soldering, but it's not really worth the hassle.
I purchased the alarm for £300 from BMW, they programmed it in and the tell-tale light wouldn't work, took it back and they had to program the instrument cluster (to get the little flashing red light to work). Mine is an ex-police bike and never had that function before, so you can see what this is indicating here - you can upgrade or change any module, so as long as they hold you by the short and curlies.
The system is all designed around the main ZFE module - there are THREE types LOW, MED, and HIGH, if you have a basic bike, you will have a LOW ZFE, if you have all the bells and whistles, including ex-Police Sirens, you need a HIGH ZFE. Although BMW says that they offer no upgrades, I know that they will work if plugged in (changed my RH handlebar unit to get BC and the heated seat control) I instantly got the function for the trip computer in the LCD, but to get the functionality of the heated seat it needs to be programmed by...BMW!
I know what you're thinking, just change the ZFE module...nope it won't work with the other modules unless it's programmed by BMW.
