Keys: The Full Story.
From the WDS for information.
Electronic Vehicle Immobilisation System EWS 3.3
The EWS 3.3 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 mounted 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 ring antenna (coil) at the ignition lock and the transponder chip integrated in the key.
The key then sends data to the EWS3 control module. If this data is correct, the EWS3 enables the starter by way of a relay installed in the control module and additionally sends a coded start enable signal via a data link to the DME/DDE.
Key with integrated transponder chip
A chip which can both transmit as well as receive (transponder) is integrated in the key. This transponder chip obtains its power from the field built up by the ring coil and uses it to communicate with the EWS3 control module. This means that no battery is necessary in the key for power supply. Every key or the transponder integrated in it is a unique part. The control module can also differentiate between the individual keys. The key transmits and receives data from/to the EWS control module.
If errors occur during communication between the EWS3 control module and the individual keys, these errors are stored in the fault memory - separate for each individual key.
The ring coil is mounted on the ignition lock and serves as an antenna for communication between the transponder chip (in the key) and control module.
EWS 3.3 control module
The EWS 3.3 control module communicates with the key mounted in the ignition lock. If the communication procedure is correct and the key has sent all data necessary for identification and start enable to the control module, the control module detects whether the key is valid and has been released for use. If this is the case, it releases the starter relay located in the control module and sends a coded enable signal via the data link to the DME/DDE.
The control module can manage a maximum of 10 keys allocated to the control module, i.e. a maximum of 6 replacement keys are possible.
The control module can identify the individual keys thus making it possible to disable/enable individual keys and to store fault codes for each individual key separately in the fault memory.
Data link to DME/DDE
The EWS3 control module sends a coded enable signal to the DME/DDE via the data link. The engine cannot be started before this signal has been transferred.
Engine control module (DME/DDE) with coded start enable input
The engine control module (DME/DDE) only enables ignition and fuel supply if a correct enable signal is received from the EWS control module.
Identical variable codes are stored in the EWS 3.3 control module and in the DME/DDE control module. The value of these codes changes after every start procedure. Engine start is only enabled when the code sent by the EWS control module agrees with the code in the DME/DDE control module.
The control modules are allocated only during initial programming of the DME/DDE control module. The engine control module then adopts the basic code of the EWS control module.
It is not possible to replace the DME/DDE or EW 3.3 control modules for test purposes!
In the case of certain faults, it is possible that the variable codes in both control modules deviate from each other. In these cases it is possible to calibrate the variable codes by means of the service function ”EWS - DME/DDE calibration”.
P/N input for automatic transmission
Whether the vehicle is equipped with automatic transmission is defined in the coding.
On automatic vehicles, a start procedure is enabled by the EWS3 only if the selector lever is in position P or N.
The EWS3 control module receives the information with regard to the selector lever position twice:
Via a data link
Via the K-bus
If the information ”selector lever in position P or N” is sent only via the K-bus but, due to a fault, not via the data link, noticeable start delays within the range of 1 - 2 s can occur.
”Central locking secured” signal
The EWS3 control module receives this information via the K-bus.
If the EWS3 control module receives the ”central locking secured” signal from the general module, in ignition lock position 1 (terminal R), the EWS sends back a signal via the K-bus which unlocks the central locking.
For safety reasons, the EWS3 control module features a code-dependent run-on time (approx. 10 seconds). It begins when the ignition lock is switched to 0 position. Within this run-on time start with any mechanically fitting key is enabled.
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 then checks the key data to ensure it is correct and only then sends an enable signal to the engine management system and starter.
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 DME/DDE control module.
Changing individual components
Replacement keys can be obtained from a sales point only via a BMW dealer where one of the 6 replacement keys fitting the vehicle is programmed. This key is not a copy of the lost key, but rather a new key.
A total of not more than 6 replacement keys suitable for the installed EWS control module can be made and handed over.
There is a noticeable start delay of 1 - 2 s when a new key is inserted in the ignition lock for the very first time. From then on, the start procedure should take place without delay.
Lost keys must be blocked by means of diagnosis. Refer to ”Special features of the diagnosis program”.
Each request for a key is documented so that inquiries from insurance companies and authorities can be followed up.
Procedure for loss of all 10 keys
A new EWS control module is required if all 10 keys are lost.
By providing all the necessary data, it is possible to obtain a new EWS control module from a BMW dealer and the new transponder keys allocated to it with the previous mechanical key code.
EWS control module
The following procedure should be adhered to when replacing the EWS 3.3 control module:
Before replacing the EWS3 control module: Leave defective control module installed in vehicle and in the coding program (Encoding ZCS) select point ”1 New coding - 1 Replace control module - 1 Read out data from defective control module”. Coding data and vehicle-specific data is read out of the EWS control module with this part of the program and buffered in the MoDiC or DIS tester.
Now install new EWS 3 control module.
After replacing the control module: Encode new EWS 3 control module with coding program selection point ”1 New coding - 1 Replace control module - 2 Transfer data to new control module and encode control module”. The buffered data is now transferred and EWS - DME/DDE calibration is carried out.
The procedure described above must be adhered to as all the data necessary for vehicle identification is also stored in the EWS control module. It will be necessary to do without the data readout from the old control module only if the EWS 3 control module no longer has diagnostic capabilities.
Proceed as follows in this case:
Install new EWS control module in the vehicle and encode with the encoding program and selection point ”1 New coding - 2 Re-encode control module”.
Then carry out matching with selection point ”EWS - DME/DDE calibration”.
In this procedure, the vehicle data necessary for automatic vehicle identification cannot be written to the EWS control module.
Replacement of engine control module (DME/DDE)
After replacing the engine control module, ”EWS - DME/DDE calibration” must be conducted with the coding program or in the diagnosis program.
The ignition must then be switched off for at least 25 s.
It is possible to disable or enable individual keys electronically via the diagnosis function (service functions).
Electronically disabled means that both the starter as well as the engine control module are not released (enabled) for the start procedure. It should be borne in mind that an electronically disabled key still fits mechanically, i.e. all flaps, lids and doors can still be opened.
Display of keys used to date in this vehicle
Here, the display shows for each one of the 10 keys which can be managed by the EWS3 control module whether it has been recognized at least once by the EWS control module, i.e. it is possible to trace, also on older vehicles, how many keys have already been used in this particular vehicle.