The EWS A.K.A (Electronic Immobilizer) is a security feature in BMW vehicles that prevents unauthorized start of the engine. EWS2 and EWS3 are different generations of this technology.

EWS2 (Electronic Immobilizer v.2) was introduced in BMW vehicles in the mid-1990s. It uses a coded transponder in the key and a reader in the ignition switch to validate the key and allow the engine to start. EWS2 is a basic immobilizer system that provides a moderate level of security against theft.

EWS3 (Electronic Immobilizer version 3) was introduced in BMW vehicles in the late 1990s. It uses a more advanced encryption algorithm to generate rolling codes that are transmitted between the key and the EWS control module. This rolling code system provides a higher level of security against theft than EWS2.

In summary, the main difference between EWS2 and EWS3 is the level of security they provide against theft. EWS3 uses a more advanced encryption algorithm that provides a higher level of security than EWS2.