Field test of 50" double row light bar.
We often get questions regarding what are CAN Bus bulbs, and why are they used in vehicles instead of standard LED bulbs. There seems to be lot of misinformation and confusion on the subject, so we want to provide a simplified explanation to help demystify CAN Bus for you.
What are CAN Bus LED bulbs?
CAN Bus LED bulbs are specifically designed with built-in load resistors to allow them to communicate with CAN(Controller Area Network) Bus equipped vehicles without triggering the on-board computer. This is because LED bulbs use so little power, and without those built-in load resistors, the computers on CAN Bus equipped vehicles may detect this as a "bulb out", and will show an error code/warning light.
NOTE: Load resistors can be used to stop CAN Bus error codes when using LED bulbs which do not have built in CAN Bus resistors.
Who invented CAN Bus, and why do we use it on vehicles?
The CAN Bus system was developed by Bosch in 1986, and quickly gained acceptance in the automotive and aerospace industries. The dual-wire network allows a vehicles electronic control units to communicate without a host computer, and greatly reduces the vast amounts of wiring previously needed to allow these controls to send data back and forth (such as vehicle speed, engine coolant temp, throttle position, switch states and so on). Simply put, think of the CAN Bus as the link between your home computer and your router/modem.
The graphic shows a simplified diagram with some of the possible units/devices that can be connected onto the CAN Bus.
CAN Bus System Schematic Diagram
1. Engine Management Electronic Control Unit
2. Transmission Electronic Control Unit
3. Anti-Lock Braking Electronic Control Unit
4. Traction Control Electronic Control Unit
5. Airbag Electronic Control Unit
6. Power Steering Electronic Control Unit
7. On-Board Diagnostic (OBD) Connector
8. Controller Area Network (CAN Bus)
In the end, all of the vehicles component inputs and outputs are controlled by a computer module, and the module uses the CAN Bus to share that information. This allows for multiple modules to share inputs and data without the need to run multiple wires to each. Ultimately, the CAN Bus provides more precise control over the vehicles systems, providing better diagnosis and better diagnostic control.
How do I know if my vehicle has a CAN Bus system? Though commonly found in European vehicles such as Audi, Mercedes-Benz, BMW, Range Rover, Volkswagen and Jaguar, American car manufacturers didn't started adopting the CAN Bus system until 2006. With that said, it doesn't necessarily mean the CAN Bus controls the vehicles lighting in those early models. In most cases, it wasn't until 2014 when CAN Bus was becoming widely used to control lighting, specifically in Ford and Chrysler vehicles.
To find out if your vehicle requires CAN Bus bulbs, we recommend researching your specific vehicle, or contacting your local car dealer to be sure. An alternative way to tell is by removing a bulb, such as from a tail light or turn signal, and drive the vehicle a short distance during the day with the exterior lights in the on position. If a an error code/warning light appears, the vehicle is equipped with CAN Bus.
You may have noticed that your 3157 or 7443 replacement bulb has a CK, SCK, SACK, SRCK after the bulb number. That means that your vehicle uses a non-standard 3157 or 7443 bulb. Though they may look the same externally, the difference is in the way the socket is wired. Only a handful of vehicles made in certain years, from a few manufacturers use a CK wired socket.
Before we get into how the sockets differ, let's look at the effects of installing the wrong bulb. Installing a CK or non-CK bulb into the opposing socket, the LEDs will not work properly or worse, they will blow your fuses that protect that specific lighting circuit. If you've already encountered one of these issues, chances are pretty good you have the incorrect bulb for the base type.
One question you may ask is 'why doesn't this affect incandescent bulbs?' Incandescent bulbs illuminate using heated coil wires that only require one positive and one negative contact. In electricity terms, they are not polarity sensitive. Polarity sensitive simply means that a bulb can only be inserted and make contact in one way to work properly (positive to positive, negative to negative). Most LED bulbs are polarity sensitive, which is why making sure you get the right bulb for the socket is important.
Though both sockets may look identical externally, the difference between the two is the position of the ground contacts in the socket. The best way to determine if your socket is wired for CK or non-CK is by using a test light or multimeter to determine which metal contacts on the socket are positive and which are negative. See the image below to compare which socket type you have.
NOTE: Remove all tail light bulbs before testing, otherwise the filament in the brake circuit will read as a "false ground".
One simple way to protect yourself from installing the wrong bulb, is to use our new 3030 Series bulbs. The new bulbs are NOT polarity sensitive, and will work in both standard, and CK wired sockets. At 950 lumens per bulb in an all aluminum housing, the 3030 Series is a win win for you and your vehicle!