I typed bits oft this in a PM the other day, but thought it may be useful to others...
Disclaimer: I am no expert. Take the below as exactly what it is: ramblings of a random bloke on t'Internet. It is a pointer to start googling and investigating further. My motive is only to offer info to try to offer some info to help fellow bikers.
So, that out of the way, EWS (Electronische Wegfahrsperre) can come up as an error for many reasons, but thinking logically... Simplistically speaking, the bike key holds a passive "chip" inside it with a code, it goes in to the antenna which [given that the electronic power is there] agitates the key chip and "reads" the code off the chip, sends it to the ECU, which, then, compares it with the stored value and allows the bike to be started if they match. So, components involved : Key, antenna, some wiring, ECU [and indirectly the battery].
So... if the low-beam stays on, there is no whirring from the idle-actuator, no pulse on the fuel pump and no gear indication on the LCD... those symptoms are the same as it the ECU [BMSK-P] was actually completely disconnected. It would then not be illogical to think that the ECU is not booting up. If you can use a multimeter, you can do some basic tests. Head to the smaller of the two ECU connectors under the seat. Disconnect it and do some continuity/voltage tests. If I remember the pinouts correctly (let me know if they are not as expected and I will double-check/correct the post for future reads):
1) Firstly, check that you are getting power to the ECU. You should have the battery voltage [~12V] across pin-3 (-) and Pin-6 (+). (Pin-34 should be the switched +12V [i.e. ON when IGN ON]). The belts-and-braces method is to wire a consumer (like a small automotive (12V) light-bulb) to those to check for the solid current under load.
2) Check you are getting good earth too.(continuity to the frame/engine/battery(=) @ pin 3) may as well check the brown cable going from the battery(-) to the engine on the left side, near the starter.
3) Since you are already at the ECU connector, If you have disconnected the ring-antenna, you may as well check the continuity to the ring antenna; Although that is unlikely to be the problem at this stage, If the theory is sound and the ECU is not booting up at all.
Pins 1234 @ ring antenna should have continuity to pins 8,43,55,57 on the smaller ECU connector, respectively. Numbers are cast into the connector but are very small. Top-tip: Use your phone camera for magnifying if your eyesight fails you in this endeavour. Ensure that there is no continuity between the ring-antenna connector pins too (in case of cables chafing against eachother)
[You may need some pins to insert into the connectors if your multimeter probes are too fat.]
If all of this is as expected, chances are the ECU has a problem and is not booting up...
Hope that helps someone...