Originally Posted by Qsilver7

There are 3 features in the remote keys and all are independent systems that work in conjunction and sometimes in tandem with each other...but all are completely different systems:

• EWS - immobilizing system...uses a transponder chip that communicates over a 125 KHz radio signal with the DME/EWS Control module/Ring Antenna (located around the ignition cylinder)/remote key. This feature is self powering (uses induction) and DOES NOT require the battery inside the key to work. But it can get out of sync with the EWS control module (the ISN rolling code)...which requires BMW diagnostic equipment (or aftermarket software/hardware) to communicate and set/reset or "sync".
• FZV - (fbzv) remote central locking...transmits a 315 MHz signal to a receiver in the vehicle which then sends that data to the GM to lock/unlock the vehicle. (requires the battery inside the key to operate)
• DWA - anti-theft alarm siren system...transmits a 315 MHz signal (433 MHz in Europe & some other markets) to a receiver in the vehicle which then sends that data to the GM to arm/disarm the vehicle. (requires the battery inside the key to operate)