E46, E39,first X5, X3 are all iBus. 1er, current X5, E60, E90 are all optical (MOST). iBus TCUs and cars are not compatible with MOST TCUs and cars. More important though is the hardware version. All but the very last TCUs and ULFs were very poor at pairing with phones not on the supported phone list. If you have an iPhone, Blackbery or Android, or something else new, you may find most TCUs won't work properly with it.