What is a CAN-BUS Alarm? How are they different?
CAN stands for Controller Area Network. BUS is an electrical term that means that every device on that BUS is connected by the same wire or wires. In other words it is a communication system between electronic control units in a vehicle where data can be sent and recieved.
The data travels down a pair of twisted wires which make up the network.
CAN-BUS explained
If you want more details then checkout Wikipedia
What advantages do CAN-BUS alarms have?
There are a large number of inputs that a car alarm needs to be effective. These include the doors, boot, bonnet, ignition, and central locking. CAN-BUS read the data for all these circuits with just 2 wires.
CAN-BUS alarm installation compared to traditional alarm installation
With a traditional PLIP upgrade alarm all of these inputs need to be connected via individual wires. Some vehicles require in excess of 20 connection points which involves running a heap of cables all over the vehicle, and splicing and soldering into each circuit.
CAN-BUS alarms: Less intrusive with more functionality
With all the input data read by tapping into the CAN-BUS there is a lot less wiring to be done. There is also the potential for extra features which are simply not possible with a PLIP alarm.
How good the features on the alarm can vary massively between vehicles and what data is available to be read. Personally I love working on German vehicles as most include window open status which can be great as shown in the video.
Most vehicle manufactures don’t like CAN-BUS data being sent to the vehicle, Most alarms I deal with only read the CAN-BUS data so there is no risk of creating error codes. All the alarm outputs such as horn and hazard light controls are wired up directly to the relevant circuits.
CAN-BUS alarm firmware
The other factor in how good a CAN-BUS alarm can be is the vehicle specific alarm firmware. I’m a big fan of Vodafone Automotive as the firmware is normally very well tested and works. They are also very good at doing updates.
I have been involved in sniffing CAN-BUS data on a number of vehicles so that alarm firmware can be programmed for new vehicles. It’s a time consuming process that to get things right, and it’s important to test that everything is perfect before it gets flashed to an alarm and installed into a vehicle.
Junk CAN-BUS alarms with poor firmware
Not all alarms are equal. There are a number of poor quality CAN-BUS alarm that get rebranded here in NZ so be warned.
As for the firmware, well if it’s not good then the alarm suffers the same pitfalls as a poorly installed PLIP alarm. I’ve seen numerous CAN-BUS alarm that don’t work well due to lazy data gathering and a lack of testing.
A list of vehicles compatible with the 8422 CAN-BUS alarm can be found here.
Understanding how the CAN-BUS firmware works with a specific vehicle
From a user point of view all you probably need to know is that the alarm arms and disarms with the factory remote. But as an installer it can be much more interesting.
Good CAN-BUS alarm installers have a deeper knowledge
If you look how an alarm arms and disarms, the way it works is often very vehicle specific. It can vary greatly between vehicle makes and models.
Take my Honda Vezel for example, the alarm arms and disarms when the remote is pressed, regardless of a door being open or closed. Here the CAN-Bus detects that the car has received the remote command.
This is good to know for trouble shooting as it’s possible to arm the alarm without the doors locking.
Most Toyota don’t arm the alarm if a door is open as the CAN-BUS is looking for a remote command and an output from the car to lock the doors. This means that if a door is left ajar then the alarm will not arm when the remote is pressed.
My previous van was a Nissan e-NV200. There was no remote data for the CAN-BUS to read so it was programmed to read the door locks and the hazard lights to arm. This is good to know as the alarm has the potential to be tricked into disarming if an inhibit is not fitted to prevent it.
Old School knowledge – Is your installer a geek?
I suggest using an installer with experience for any alarm installation. Just ask them the question “What is a CAN-BUS alarm?” and “how will it work on my vehicle?”
If the installer has a passion for their trade you’ll get a better install and support should you need it.
