What is CAN bus, how it works and how it affects you when you want to add electrical accessories or make other changes to the electronic systems / electrics of your BMW R1200GS motorcycle.

CANbus technology has been used in automotive industry for some years. CAN (Controller Area Network) was developed by Bosch in the early 1980's and became an international standard (ISO 11898) in 1994. It was specially developed for fast serial data exchange between electronic controllers in motor vehicles.

I believe that the introduction of the on-board single-wire network system in 2004 for the BMW R1200 range of motorcycles is BMW Motorrad's first use of this 'technology' (if you know different please let me know!). However Ducati was the first motorcycle manufacturer to use CAN-bus in a production motorcycle in 2002. The Ducati 999 uses the two-wire digital bus to simplify the electrical system and reduce weight significantly which no doubt is why BMW adopted the system.

Controller–area network (CAN or CAN bus) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer.

An electrical bus (sometimes spelt buss) is a physical electrical interface where many devices share the same electric connection.

BMW R1200 / R1200GS CAN bus System - What BMW say...
On-board network - CAN bus technology: With fewer cables than ever, the new on-board network ensures a high standard of reliability plus an even wider range of functions. The single-wire system transmits all relevant data via one single wire to the respective control units. Physically, it is a double-wire system with CAN bus (Controller Area Network) technology consistently interconnecting all control units and the central vehicle electronics (CVE) to form a permanent data network - the various units exchanging data with each other. Apart from simplifying the main wiring harness it also allows efficient, comprehensive diagnosis of all vehicle functions.
 

A further advantage is that the system no longer requires conventional fuses. CAN bus technology automatically switches off the suspect component - where possible - and checks whether the function is still defective when the rider again starts the motorcycle. The network also serves to feed all data to the cockpit display on the info-flat-screen. To easily adapt and integrate electronic accessories into the on-board network, there is a plug for special equipment.

Adding electrical accessories / power for electronic items (car fog lights, spot light, HID ballasts, heated clothing etc)

You'll have to avoid taking power direct from CAN Bus controlled systems as the additional power draw will trigger a system fault. The CAN bus systems are programmed for certain limits on current draw so it's best to install a relay which will be triggered/switched via the CAN bus system (e.g. headlamp wiring for additional spotlights) and power to the accessory direct from the battery via a fuse. If you intend to install a number of accessories that require power an auxiliary power / fuse panel such as the Centech AP1 or Touratech TPS 15 should be used.

Here is the wiring diagram I made up and used. Note that I have the GPS wired directly to the battery still, since I want power at all times. If you have a unit with a battery, you can use the fuse box.

Lots of wires can be messy, but BMW was thinking about us when they elected to furnish a tool kit with no tools in it (for all intents and purposes), so I put the fuse box in the spote where the tools used to be. It is the perfect location.