A pretty good article on subject systems. Something to think about the next time someone is making modifications to lights or other systems on your bike.

"It seems everything has become increasingly computerized in the past decade or so. We have everything from network-connected refrigerators to pet feeders you can monitor from across the globe and cars that drive themselves (until they don’t).

Naturally, our motorcycles have followed suit. Gone are the days of cleaning your ignition points and your pilot jets to keep your ol’ BSA going.

Thanks to decades of engineering iteration, vehicles are more complex than ever. Instead of one or two computers, most modern vehicles are equipped with an array of control units that are individually responsible for systems such as engine management, anti-lock braking, traction control, and chassis systems.

These computer modules work in unison to conduct a symphony of ones and zeros, transferring information between each other to keep things running as intended.

It’s All About Communication

With some vehicles having more than 100 individual control units, manufacturers needed an efficient system for them to communicate with each other. Enter the CAN bus standard.

All these control modules utilize a standardized networking communication protocol called controller area network (CAN) bus to transmit and receive data in real time. The CAN system is able to link each of a vehicle’s computers over a network of just two wires.

Think of it as the central nervous system of the machine.

A motorcycle’s electronic components, like the engine control unit (ECU), ABS module, and display unit, can communicate with each other by sending and receiving messages through the CAN bus. Messages can range from simple status updates (such as speed or throttle position) to more complex things, like detailed error messages or specific control commands from one module to another.

For example, let’s picture a scenario where the traction control module detects wheel slip. It immediately sends a dispatch to the ECU to cut power to the rear wheel until traction is regained, at which point power output returns to normal.

All this happens seamlessly in mere fractions of a second, often with the high-horsepower machine’s pilot oblivious to the life-saving intervention—save for the TC light blinking away on the dash.

Shiny Sides Up

The main advantage of the CAN bus system is, as I mentioned above, real-time communication. This is what makes features such as sophisticated, lean-sensitive ABS or traction control that require high-speed communication and feedback between components possible.

Another advantage, believe it or not, is reduced complexity. The two-wire system replaces the multitude of individual cables that would be required to connect each computer individually, thus cutting weight and saving space.

Finally, in diagnostics and troubleshooting, mechanics often have a much easier time when they can connect diagnostic tools to the CAN system to read error codes, monitor sensor data, and identify potential issues within the motorcycle's systems quickly and accurately.

Rubber Sides Down

But can the CAN have disadvantages? Well, although it often benefits mechanics with the proprietary diagnostics software, it’s obviously not as easy as popping your float bowl off your carburetor and blowing it out with some carb cleaner to get you back on the road when something does go wrong.

Another problem—as many riders are likely already aware—is the CAN bus system’s extreme sensitivity to change. Trying to power a GPS or phone charger from the wrong wire or even installing turn signals with significantly different power requirements to the factory ones can cause problems with the CAN system, including mysterious error codes or disabling the bike altogether in extreme cases.

This is because CAN works on a very narrow and specific voltage range and utilizes changes in voltage to carry messages between components. Changing power draw in either direction can adversely affect these messages and suddenly they’re all Greek to the CAN system, generating error codes.

Next time you want to install auxiliary lights or a louder horn, you’ll have to do your homework to see if your bike uses CAN bus. Some machines even monitor the status of your turn signals and something as simple as upgrading your indicators could cause a CAN bus fault.

Many motorcycles come equipped with accessory circuits specifically to avoid these situations. If you don’t have that option, some other workarounds include CAN-friendly accessories that are designed with your bike in mind or separate control modules that work with a CAN system and will not interfere with its operation.

Unfortunately, aftermarket manufacturers are not always clear about whether their products will play nicely with CAN, so some digging may be required. Often, if you have an issue, the computer will point you in the correct direction via the display. That’s not guaranteed, though, and a trip to your dealer may be in your future if you get really stuck.

If you’re electrically accessorizing something like a new BMW R 1300 GS, I’d suggest doing one thing at a time if you’re not 100% sure of compatibility. That way you can easily go back and remedy the issue if one does present itself.

We CAN’t Have it All

Overall, the advantages of CAN bus make it a reliable and efficient communication protocol for managing the complex electronic systems in modern motorcycles. It contributes to better performance, safety, and user experience.

While it is true that our bikes have become more complex and often can’t be serviced without at least some help from the dealer, on the whole, systems like CAN bus make for a better overall user experience.

The high-speed and data-dense communication make sophisticated systems such as dynamic suspension control, high-performance ABS, lean-sensitive traction control systems, and stability control systems possible. Without CAN bus technology, we wouldn’t have the spectacular machines we have come to love from today’s motorcycle market.

So, for now, CAN bus is an automotive industry standard that’s here to stay—at least until someone comes up with the next, better standard.