CANBus Decoders and HID Lights

How CANBus Decoders affect your HID installation, and what you need to know to prevent dash warning lights.

What is a CANBus decoder?

A CANBus decoder in simple terms, is a device that tells the vehicle's diagnostics controller (ECU unit) that the lights are on and running; as well as, avoid pulsating lights and bulb-out warnings on your dash.  A common problem is that the vehicle will attempt to "restart" a headlight as a check to see if they are working correctly which results in a rhythmic pulsation (on/off) of your lights. To truly understand the functions of a CANBus decoder, we must first understand the role of the CANBus network in an automotive electrical system and how it operates.  CANBus, or Controller Area Network (Bus meaning pathway or data transfer channel) is a communication standard created by Bosch for automotive, industrial, and medical devices. CANBus networks are utilized where devices (CANBus nodes) can all use the same pathway/channel to speak to one central CANBus controller.  CAN is one of the five supported standards of vehicle diagnostics in today's OBD-II (On Board Diagnostics).




In today's vehicles, there are several ECU (Electronic Control Units) for the many subsystems in a vehicle today.  Your headlights (if CANBus sensor equipped), engine, A/C system, airbags, door locks, TPMS (Tire Pressure Monitoring System), etc. all are either independently operated with an ECU, or work together to operate your vehicle.  Each ECU node needs to communicate with other devices or the vehicle as a whole to properly perform the functions you request.  How do all these systems communicate with one another to determine what needs to be done?  You guessed it, the CAN-Bus network.

Who cares, why would I need it for my HID upgrade?
Some vehicles use sensors on their headlight power wires which connect to the CANBus network to monitor headlight functionality and report bulb-out situations. Typically, if the output voltage and/or output wattage on the wire is less than 12.8V and 55W, this triggers the ECU that is monitoring those power wires to send a signal to the CANBus controller letting it know the bulbs are out/defective.  This in turn will trigger the dash warning light notifying you a bulb is out.  An HID system consumes less power than a halogen system, so when converting to HID, the ECU will report only 35W power consumption which often times is less than the minimum threshold of the sensor's controllers acceptable limit, and triggers the bulb-out warning.


I want to install HIDs on my vehicle, do I need a Premium CANBus decoder equipped XenonSupply ballast?
Typically, luxury vehicles with more complex electrical systems will require the use of the CANBus decoder equipped ballasts.  Many of our German imports (BMW, Mercedes-Benz, Audi) use sensors on the headlights that report to the CANBus network.  Other manufacturers such as Honda/Acura and Toyota/Lexus/Scion do not and use a simple on/off sensor to determine whether the lights are operating correctly, separate of the CANBus network.  As our knowledge base continually updates for vehicles that require CANBus or vehicles that do not require CANBus, you will need to contact our support team if you are not confident which type of ballast you need.  One of our support technicians will be able to give you the best recommendation based on your vehicle year, make, and model.

XenonSupply Premium CANBus Equipped 35W Digital AC Ballast XenonSupply Premium Slim CANBus Equipped 35W Digital AC Ballast
Premium CANBus decoder ballast HID Xenon Headlight


When in doubt, use CANBus decoder equipped ballasts!
Having a CANBus decoder equipped ballast can only help you when installing HIDs.  A CANBus decoder equipped ballast will operate with a non-CANBus lighting system perfectly so having the additional feature and not using it is better than needing it and not having it.  The CANBus ballasts are also manufactured with higher quality components to perform more efficiently than standard non-CANBus ballasts.  To put it in a long-term perspective, if you ever switch to a newer vehicle you can transfer the ballasts to that vehicle because chances are it will have a CANBus equipped headlight sensor.  Newer vehicles are more likely to use CANBus sensors on the headlights as the technology becomes cheaper to manufacture and implement.

What if you bought a CANBus equipped ballast and still have errors on your dash?
Are you using a kit with a relay harness or Bi-Xenon bulb?  Bi-Xenon kits use a wiring harness that pulls power directly from the battery which means the stock connector is not using anywhere close to the 55W it normally puts out. The Relay in this harness uses a fraction of the power to activate a switch that, in turn, pulls power directly from the battery.  Safer for the vehicle, not so good for your CANBus issues.  In addition, these types of harnesses usually leave the passenger side, or the opposite side of the battery with an empty headlight connector which also is not good for CANBus sensors.  You will require a pigtail, shown to the right, to connect in the empty factory connector to add resistors to the relay side socket to boost power consumption up to 55W. This type of installation will require direct communication with a XenonSupply technical support representative as parts are determined on a case-by-case basis.

If you have any additional questions regarding CANBus decoders and their application with your vehicle please email or call us at or toll-free at 1-800-840-3240.
XS Team
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