What is the yellow wire with black stripe on the back of a Pioneer DEH p6400?

The yellow wire with a black stripe on the back of a Pioneer DEH-P6400 is typically the illumination wire. This wire is used to connect the car's dashboard lights to the stereo, allowing the unit to dim or brighten in accordance with the vehicle's lighting settings. Properly connecting this wire can enhance visibility and aesthetics during nighttime driving. Always refer to the specific wiring diagram for your model to confirm its function.