in the old tail light you have 2 bulbs which both light at 50% intensity when low beam is ON and at 100% when you hit the brakes. the facelift tail light has separate circuits for sidelight and brakes so requires separate signals on the wires. if you connect the led taillights, the old controller will output 7 volts on both wires so side light led and brake light will be ON all the times at half intensity and when you hit brakes will go to 100%. this is hardly visible in sun light. i guess the adapter module will "listen" to the voltage supplied by the controller and will issue separate voltage on each wire to the tail light for their respective function. there are now errors in DIS when you connect the led tail lights with old controller but when ignition is ON, the controller issues on all circuits a 5 volts pulse every 30 seconds to check bulb integrity which will result in a short flash in the led tail light. somebody driving behind you will think that you press brakes and hazard warning lights briefly every 30 seconds which is anoying and in many countries illegal as it is considered a malfunction of the car's lighting system.