Car Access System (CAS) Control Module: Notes

The CAS serves as an antitheft alarm system and enables the start of BMW vehicles.

A transponder chip is integrated in each of the vehicle keys. A ring coil is fitted about the ignition lock. The transponder chip is powered by this coil from the CAS control module. This means that no battery is necessary in the key. The power supply and data transfer take place in the same way as a transformer between the loop antenna (coil) at the ignition lock and the transponder chip.

The key then sends data to the CAS control module. If these data are correct, the CAS control module enables the starter by means of a relay located in the control module and additionally sends a coded start enable signal via a data link to the DME/DDE. These procedures may result in a start delay of up to half a second.