May help to understand the E46 EWS system:
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 fitted about the ignition lock. The transponder chip is powered by the EWS3 control unit 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 unit. If this data is correct, the EWS3 enables the starter by way of a relay installed in the control unit and additionally sends a coded start enable signal via a data link to the DME/DDE.
<h2 class="chapter">Components</h2> <h3 class="subsection2">Key with integrated transponder chip</h3> 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 unit. 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 unit can also differentiate between the individual keys. The key transmits and receives data from/to the EWS control unit.
If errors occur during communication between the EWS3 control unit and the individual keys, these errors are stored in the fault code memory - separate for each individual key.
<h3 class="subsection2">Ring coil</h3> The ring coil is fitted on the ignition lock and serves as an antenna for communication between the transponder chip (in the key) and control unit.
<h3 class="subsection2">EWS 3.3 control unit</h3> The EWS 3.3 control unit communicates with the key fitted 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 unit, the control unit 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 unit and sends a coded enable signal via the data link to the DME/DDE.
The control unit can manage a maximum of 10 keys allocated to the control unit, i.e. a maximum of 6 replacement keys are possible.
The control unit 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 code memory.
<h3 class="subsection2">Data link to DME/DDE</h3> The EWS3 control unit sends a coded enable signal to the DME/DDE via the data link. The engine cannot be started before this signal has been transferred.
<h3 class="subsection2">Engine control unit (DME/DDE) with coded start enable input</h3> The engine control unit (DME/DDE) only enables ignition and fuel supply if a correct enable signal is received from the EWS control unit.
<h3 class="subsection2">EWS-DME/DDE interface</h3> Identical variable codes are stored in the EWS 3.3 control unit and in the DME/DDE control unit. The value of these codes changes after every start procedure. Engine start is only enabled when the code sent by the EWS control unit agrees with the code in the DME/DDE control unit.
The control units are allocated only during initial programming of the DME/DDE control unit. The engine control unit then adopts the basic code of the EWS control unit.
Important
It is not possible to replace the DME/DDE or EW 3.3 control units for test purposes!
In the case of certain faults, it is possible that the variable codes in both control units deviate from each other. In these cases it is possible to match the variable codes by means of the service function â€EWS - DME/DDE matchingâ€.
<h2 class="chapter">Influencing variables</h2> <h3 class="subsection2">P/N input for automatic transmission</h3> 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 unit receives the information with regard to the selector lever position twice:
Via a data link
Via the K-bus
If the information â€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. <h3 class="subsection2">â€Central locking secured†signal</h3> The EWS3 control unit receives this information via the K-bus.
If the EWS3 control unit receives the â€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.
<h3 class="subsection2">Afterrunning time</h3> Important
For safety reasons, the EWS3 control unit features a code-dependent afterrunning time (approx. 10 seconds). It begins when the ignition lock is switched to 0 position. Within this afterrunning time start with any mechanically fitting key is enabled.
<h2 class="chapter">Key identification and start procedure</h2> 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 unit.
The EWS3 control unit 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 unit 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 unit.
<h2 class="chapter">Changing individual components</h2> <h3 class="subsection2">Key</h3> 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 unit 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 â€Special features of the diagnosis programâ€.
CAUTION!
Every request for a key is documented so that enquiries from insurance companies and authorities can be followed up.
<h3 class="subsection2">Procedure for loss of all 10 keys</h3> A new EWS control unit is required if all 10 keys are lost.
By providing all the necessary data, it is possible to obtain a new EWS control unit from a BMW dealer and the new transponder keys allocated to it with the previous mechanical key code.
<h3 class="subsection2">EWS control unit</h3> The following procedure should be adhered to when replacing the EWS 3.3 control unit:
Before replacing the EWS3 control unit: Leave defective control unit installed in vehicle and in the coding program (Encoding ZCS) select point â€1 New coding - 1 Replace control unit - 1 Read out data from defective control unitâ€. Coding data and vehicle-specific data is read out of the EWS control unit with this part of the program and buffered in the MoDiC or DIS tester.
Now install new EWS 3 control unit.
After replacing the control unit: Encode new EWS 3 control unit with coding program selection point â€1 New coding - 1 Replace control unit - 2 Transfer data to new control unit and encode control unitâ€. The buffered data is now transferred and EWS - DME/DDE matching is carried out.
Note The procedure described above must be adhered to as all the data necessary for vehicle identification is also stored in the EWS control unit. It will be necessary to do without the data readout from the old control unit only if the EWS 3 control unit no longer has diagnostic capabilities.
Proceed as follows in this case:
Install new EWS control unit in the vehicle and encode with the encoding program and selection point â€1 New coding - 2 Re-encode control unitâ€.
Then carry out matching with selection point â€EWS - DME/DDE matchingâ€.
In this procedure, the vehicle data necessary for automatic vehicle identification cannot be written to the EWS control unit.
<h3 class="subsection2">Replacement of engine control unit (DME/DDE)</h3> After replacing the engine control unit, â€EWS - DME/DDE matching†must be conducted with the coding program or in the diagnosis program. Important
The ignition must then be switched off for at least 25 s.
<h2 class="chapter">Service functions</h2> <h3 class="subsection2">Disable/enable key</h3> It is possible to disable or enable individual keys electronically via the diagnosis function (service functions).
Important
Electronically disabled means that both the starter as well as the engine control unit 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.
<h3 class="subsection2">Display of keys used to date in this vehicle</h3> Here, the display shows for each one of the 10 keys which can be managed by the EWS3 control unit whether it has been recognised at least once by the EWS control unit, i.e. it is possible to trace, also on older vehicles, how many keys have already been used in this particular vehicle.
[End]
So if you want to remove the EWS you need to do the following:
Trick the DME in thinking that an EWS is installed. To do this you will have to emulate the code sent by the EWS control unit to the DME (which changes every time the engine is started)
The only way to do this is with a replacement control unit to emulate the EWS, or replacing the DME with an aftermarket DME that has no EWS dependency
I do not know if such devices exist, and I do not know if such and approach will be successful.
But you have stated the customer wants to retain the original DME.
So you have no choice but to fit the EWS.
I strongly suggest you get a copy of the BMW WDS (Wiring Diagram System), which is where I obtained the above description.
This describes the EWS, and the DME, and you will know exactly what each wire colour is for and where it goes.
I cannot imagine doing what you are doing without using the WDS....
Good luck!