CAN connecting tips for installers
Connecting an interface or other device to a CAN-Bus requires some special attention. Here are some valuable advises and guidelines brought together in order to assist you.
The CAN-Bus shall never be used as a source for electrical current! The CAN-Bus network is capable of delivering only a few milliamps, hence every externally connected device will directly influence the voltage levels on the CAN-Bus and consequently its overall performance.
Make absolutely sure the device to be connected has its own power supply!
Location of the connection
The general idea that the data carried by the CAN-bus is the same throughout the entire vehicle is certainly at least not always true. Many vehicles are equipped with several so-called CAN Gateways. These Gateways can either manipulate or even block selected data. Hence, the data before and after such a Gateway may be different although the colour of the wiring remains perhaps the same, which in turn will increase the confusion even more. Before making any connection, check out the connections in the In-car instruction. These are always tested and approved.
The CAN-Bus in a vehicle, like any other electronic circuit, represents a specific resistance or, better still, impedance which is determined amongst other things by the length of the wiring harness of that specific car model and it makes a balanced circuit. For this reason it is of the utmost importance to keep the wiring of the device to be connected as short as possible.
To establish the connection between the CAN-Bus and the new device soldering is the commonly applied method. An error often made here is to use an electric soldering iron to do the job. Wherever an electric current is running it inevitably induces an electric field. To obtain the high soldering temperature needed these irons require relatively high currents inducing an equally high electrical field. This field may very well interfere with the data on the CAN-Bus or any other electrical circuit in the vehicle, which may cause all sorts of unforeseen and many times even untraceable errors. The sound advice therefore is to always use a gas-heated soldering iron!
Whenever you make a connection to the CAN-Bus it is absolutely preferable to wait until the CAN-Bus is no longer active. Even when making the connection extremely careful it still can happen unintended that i.e. a brief shortcut is made resulting in a CAN-Bus error code send to the vehicle’s board computer and stored there. Eventually and even after some time these error codes can lead to some serious and costly damage such as reduced motor performance or even coming to a complete halt and perhaps even requiring a reset of the vehicle’s board omputer system. Avoid working on an active CAN-Bus system, measure for data activity before you start making any connection.