Electronic Vehicle Immobilization System EWS 3.3

Electronic Vehicle Immobilization System EWS 3.3

The EWS 3.3 serves as an antitheft system and enables 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 the EWS3 control module via this coil, i.e. no battery is required 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 EWS3 control module. If these data are correct, the EWS 3 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 [1][2]DME/DDE. These procedures may result in a start delay of up to half a second.

Components

Data link to [1][2]DME/DDE

The EWS3 control module sends a coded enable signal to the [1][2]DME/DDE via the data link. The engine cannot be started before this signal has been transferred.

Engine control module ([1][2]DME/DDE) with coded start enable input

The engine control module ([1][2]DME/DDE) only enables engine start if a correct enable signal is received from the EWS control module.

EWS-[1][2]DME/DDE interface

Identical variable codes are stored in the EWS 3.3 control module and in the [1][2]DME/DDE control module. The value of these codes changes after every start procedure. Start enable only takes place if the code sent by the EWS control module agrees with the code calculated in the DME/DDE control module.
The control modules are allocated only during initial programming of the [1][2]DME/DDE control module. The engine control module then adopts the basic code of the EWS control module.
Important
It is not possible to replace the [1][2]DME/DDE or EW 3.3 control modules for test purposes!
In rare cases, it is possible that the variable codes in both control modules deviate from each other. In these cases, it is possible to reset both codes to the initial value via the service function [1][2]DME(DDE) EWS III calibration.

Key identification and start procedure

The following procedure takes place after inserting the vehicle key in the ignition lock:
* The transponder in the key is powered via the loop antenna and sends the key data to the EWS3 control module.
* The EWS3 control module checks the key data to ensure it is correct and only then sends an enable signal to the starter.
* The EWS3 control module sends the variable code to [1][2]DME/DDE. There, the variable code is checked against the saved variable code; if they match, the fuel injection is released.
* After the engine has started, the EWS3 control module generates new key data (change code) and transfers them to the transponder in the key.
* A new variable code is also created and stored in the [1][2]DME/DDE control module.

Fault recognition in engine control module

The following faults are monitored in the engine control module:
* Interface, i.e. line to EWS control module: In this case, the check is carried out in order to establish whether a signal is received and whether this signal is not subject to excessive interference.
* Variable code: A check is conducted as to whether the variable code which is sent by the EWS control module agrees with the value calculated in the [1][2]DME(DDE) control module.
Engine start is inhibited if a fault is detected.