What is AUX IN?
AUX IN ( Auxiliary) is the port for the audio input interface, it is 3.5mm port.
In the package of our BMW Android screen, there is an AUX Cable (photo showed as below). The function of this AUX cable is to switch the Audio from the BMW Android screen to factory car speakers. Because the BMW Android screen doesn't have the amplifier inside, it needs to use the BMW factory sound system, thus it needs to connect the AUX cable, otherwise, it will no sound output.
PS: For the car made in 2017-2018 (with EVO menu), it doesn't have AUX IN, they have a USB port. Thus the BMW Android screen without AUX cable, the sound goes via USB.
How to connect the AUX cable?
Please kindly check the wiring diagram below. The AUX cable, one side connect to the AUX port (Audio out) from the new power harness, the other side is connected to the AUX IN port under the armrest box (For most of BMW car, the AUX IN port under the armrest.