Cable harness kit S60 - 13-pin 30763 865 + Trailer module S60 30744 321 + Application1 13-pin 30764 681 The trailer module is designed to manage the electrical connections between the vehicle and the trailer regarding: Direction indicators Brake lights Position lights Reversing light Fog lights +12 V voltage The control modules stores any diagnostic trouble codes. The application number corresponds to the type of socket on the cable harness for towbar.