You hear us recommending certain lighting systems for European vehicles, Dodge, Ford, Chrysler, and Jeep; and telling most others to choose whichever kit they prefer. More specifically, if you drive one of the aforementioned vehicles, we recommend a Canbus HID kit (if choosing HID's), or Decoders with your LED kit (if choosing LED's).
Well when an HID or LED kit is advertised as "CANBUS", it means the ballast input wires have modules to provide extra resistance to the vehicle's circuit. Since HID and LED bulbs consume far less actual power than the halogen bulbs they replace; problems can arise when installed on a vehicle with CANBUS systems, which monitor if a particular bulb is working.
CAN stands for “Controller Area Network” and BUS meaning pathway or data transfer channel. Canbus systems allow different components to communicate with one another without requiring a central computer. Basically, a vehicle that comes with a Canbus system helps to notify the driver when something is wrong, it also monitors that a particular bulb is working. This can cause a problem when replacing a traditional light bulb with an LED or an HID system because they will not read the same to the CANBUS controller (as they use less power) and will assume the light bulb is burnt out, resulting in an error message being displayed to the driver, a flickering problem, or no power being delivered at all.
If it detects this lower power consumption, the lights will likely just flicker on and off. Using Canbus ballasts on an HID kit (as opposed to standard ballasts) or Decoders on an LED kit usually (but not always) provides enough resistance to overcome the vehicle's sensors. Some vehicles require just a little bit of resistance, but some outliers require exactly the same resistance as factory.
In these cases, an HID relay harness would be installed to an existing HID kit, which will have your battery power the lights instead. Load resistors might also need to be installed (applicable to both HID and LED's). Resistors help the lights consume more power and replicate factory power consumption. They are a popular and universal fix to add more power to the circuit, but not required >95% of the time.
In general, we recommend CANBUS lights to European cars, Ford, Dodge, Chrysler, and Jeep. It's important to note that this list is not exclusive, they are just the most common vehicles we see with these Canbus issues.