Flat 4 Pin Connector Wiring Diagram. It is the 4 pin connector. You must check the trailer manual to see if the wiring is correct but normally the white wire is called the ground wire while the brown wire is used for tail lights.
It is the 4 pin connector. The white wire must be attached to the trailer for the grounding and power supply of the lights. The most common 4 wire connector is the 4 pin flat connector as shown here.
Injunction of two wires is usually indicated by black dot at the junction of two lines.
It may transfer electricity better hence the connector is suggested for higher level electric in the auto. This kind of connector is perfect for customer trailers. It should not be carrying significant loads throughout the journey. Wiring diagram pics detail.