An increasing number of manufacturers are employing CAN Bus systems for managing the electrical inputs on modern-day vehicles. Historically, the reserve of high-end, high-spec models, CAN is becoming more prevalent, but there are systems available which interpret the CAN Bus signals to ensure any auxiliary light installation works as seamlessly as if fitted alongside a more traditional electrical system.

Let’s take a closer look and understand…


Audi A6 Avant - Linear-18 (CAN bus)


What is Can Bus Technology?

CAN (Control Area Network) enables communication between different systems (or Electronic Control Units – ECUs) on the vehicle, without the need for complex wiring. In operating via a central system, this allows all the different ECUs to work together effectively and efficiently; for example, the engine reports the vehicle’s speed to the transmission, which in turn must tell other modules when to shift gears. Connecting all these individual modules to each other became too complex, so a central networking system became necessary to efficiently run the vehicle.

Vehicle Electrical Systems


For vehicle manufacturers and owners there are a number of advantages to working this way, including: lighter vehicles, simplified and more easily regulated electrics, issues are more identifiable and can be isolated, and the system as a whole is more cost-effective and reliable.


How the CAN Communication Works?

CAN is a peer-to-peer network. This means that there is no master that controls when individual nodes have access to read and write data on the CAN bus. When a CAN node is ready to transmit data, it checks to see if the bus is busy and then simply writes a CAN ‘frame’ onto the network. The frame being written is essentially the signal for the CAN and other ECUs on the network to interpret; of course the specific frame being transmitted from one ECU won’t be relevant for all others, so each ECU recognises whether to essentially accept or reject the frame being transmitted. The CAN prioritises ECUs so that multiple frames aren’t being transmitted all at the same time.

So why does CAN matter when fitting Auxiliary Lighting?

Historically (and indeed still for most vehicles) standard headlamps received a 12V signal for when the lights needed to activate. With CAN, this 12V signal may be replaced by a different type of signal, in the form of the CAN frame, which the auxiliary lights can’t interpret properly. Typically, this causes the auxiliary lights to flash rapidly or not activate at all.

How do I know if I need a CanM8 High Beam Interface?

First off, just because your vehicle has a CAN Bus system doesn’t necessarily mean you’ll run into any problems. A lot of vehicles using CAN, still send a 12V signal to the headlamps when the High Beam activates for example. If this 12V signal is available, it will cause the 12V relay in our wiring kits to activate and the lamps will work like normal. Note – it’s important when testing the strength of the signal to the back of the headlamps that you identify the correct wire/pin for the high beam, and check the signal strength on/off by having another person flash the lights, not by leaving the high beam in the permanently on/off position.

If the strength of the signal to the high beam is less than 12V then a CAN Bus interface to interpret the CAN frame is needed. Our recommended solution is the Highbeam Interface from CanM8 –

How and where do I fit the CanM8 Highbeam Interface?

The video below explains the installation process:


Will fitting the Interface void my manufacturer’s warranty?

During the installation process, care needs to be taken as you will be connecting wires directly on to important vehicle systems. The vehicle warranty will be unaffected, so long as the installation has been carried out correctly, without damaging the surrounding systems. If you’re unsure, get the help of a qualified auto electrician.

Another option is the CanM8 Contactless Reader which allows the CAN Bus interface to read vehicle CAN Bus data without any actual metal to metal connection. The reader is secured around a section of the vehicle CAN Bus wiring and data is read by an induction method.

Where do I find out more about the installation for my specific vehicle make/model?

Your local vehicle dealership will ordinarily be able to advise you on the location of the CAN module, the relevant coloured wires from the CAN, and specifically which wires relate to CAN Hi and CAN Lo. You are of course welcome to enquire with us directly, or through CanM8 themselves for advice on your specific vehicle installation. In the near future, users of CANM8 hardware will benefit from even greater availability of installation guidelines and support…watch this space.