hey buddy i know its a bit late but for everyone interested in this this is not a software thing first you need to get a electromagnetic lock and the electric handle for the trunk (the wires for these are already in) and then you need to solder a missing relay and a diode to the body computer and it...

i think the sensor would be in the side mirror and hard to add if you want to search for it you can try here http://4cardata.info/elearn/169/2

it has the wiring and it is in the control unit too but it has to be activated i would love to see this feature too