From a 1200GS Technical Training manual.
Immobilizer code data structure.
The codes used during the handshake are generated from an Immobilizer Rolling Code table assigned to the VIN at the time of manufacturing. The BMS-K and corresponding ignition keys are encoded with this unique data making them an electronically mated pair for one particular motorcycle. The code table provides the codes for each key and a source for BMS-K to check the generated code for each key. Of the three [transponder] keys supplied with a new motorcycle, each one is uniquely identified (key #, ie: 1, 2, or 3). Each key additionally then has a unique immobilizer code.
During the key on sequence, the BMS-K first identifies the key sending the code data and then confirms the transmitted immobilizer code for that key. There is the possibility of a maximum of ten keys per system possible. However they must be ordered specifically by the VIN, and activated with the GT1.
Comes with three keys. How many people received their three keys?
Someone posted a while back about Honda immobilizers, and I think Harley Davidson and Ducati too, can be switched off with some code combination of switch presses, of the turn signals or brake lever for instance. Each bike having a different code. The manual 'switch off immobilizer' code based on the vehicle VIN is a fit, and also complies with the DOT immobilizer regulations of passive arming.
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Hey, speaking of EWS antennas, go out and try to start your bike with the antenna unplugged.
John (Jpalamar) was kind enough to send me a 1200 ECU and transponder key.
From looking at the circuitry in the ECU board, the pair of communication leads to the EWS antenna seem like they might be a CANbus interface. Separate though, from the CANbus network on the rest of the bike.
If the comm leads to the EWS antenna are CANbus, then if the EWS is unplugged, the pair of leads may need a 120ohm terminating resistor.
Maybe the bike will start without the EWS antenna. But it might need a terminating resistor on the data leads.
It's a thought anyway
I mean, there are security screws on the EWS, and I think those are separate from the security screws on the ignition switch. Maybe the ECU will let the bike start without the EWS antenna circuitry. No EWS antenna (but with a terminating resistor in it's stead) is different than a defective EWS.
So maybe unplugging the EWS and adding a termination resistor will do the trick.