UNIVERSAL harness with module - functionally extended harnesses, necessary during installation in most vehicles of German manufacturers produced after 2000, initially the cars had only CHECK CONTROL function consisting of control of burnt out bulbs and showing the icon on the dashboard. The next step was the introduction of a digital CAN-Bus protocol - the module also performs a number of other functions, but about this in the following section on functionality. The modules are based on relays (U1L) or the more advanced ones on processors (U2P, U3P).