EWS II Principle of Operation

EWS II verifies

EWS II sends

The transponder releases

The transponder stores

The starting sequence involves communication between all the components of the system.
Any break-down in the communication process will result in a no start condition. The sequence of events for vehicle starting is as follows:
• The key is inserted into the lock cylinder and switched (ON). The transmitter/receiver module is powered through KL R. The transmitter/receiver module sends a 125 kHz.
AM signal to the ring antenna. The AM signal induces voltage in the key coil and powers up the transponder.
• Powered up, the key transponder sends the key identification code to the transmitter/ receiver module via the 125 kHz AM signal (1). The transmitter/receiver module converts the AM signal to a digital signal and sends it to the EWS II control module (2).
• The EWS II control module verifies the key identification code and checks to see if the key is enabled (3).
• Upon accepting the key as valid and enabled the EWS II control module sends a digital password (4) to the transmitter/receiver module, which converts the data to an AM signal (5) and sends it to the transponder via the ring antenna (6).
If the transponder accepts the password as correct the transponder releases the changing code (7) to the transmitter/receiver module which converts this AM signal to digital (8) and sends it to the EWS II module (9).
• If the changing code received by the EWS II module is correct, the status of the BC, transmission range switch and TD is examined. With correct input status the internal starter relay is energized and the starter motor begins to operate (10). At the same time the EWS II module sends the ISN to the DME via the single wire communication link (11).
• If the ISN code stored in the EWS II module matches that of the DME, the drive away protection is cancelled and injection and ignition is enabled.
• During the process of sending the ISN to the DME, the EWS II module sends a new changing code to the transponder through the transmitter/receiver and ring antenna.
The transponder stores the changing code until the next starting sequence.

is one of the best Professional scan tools to for BMW; Autohex allows you to diagnose, code, program/flash ecus, replace with used ECUs, and add new keys for BMW. For more information: BMW Scan Tool