Fully functional unit. This unit basically controls or works as a passthrough for every light in the car. If you are having lighting issues, this is generally the problem. This fits some 5 Series (89-95, E34) and 7 Series (88-94, E32) and E30 BMW's. Including 528i 535i 535is 540is 730i 735is 740i 740is 750li 750 Thanks for looking!