The invention relates to an assembly module (20) for a motor vehicle, comprising an optical sensor system (30), which can be used to a) monitor a detection area (21) on the outside of the motor vehicle (1) in order to determine the proximity of a user (10), b) in the event a user (10) is detected in the detection area (21), a signal for starting an authentication test between an ID transmitter (13) and an access control system (14) of the motor vehicle (1) is triggered.