This FD02SR allows you to replace your factory OEM stereo while retaining factory steering wheel controls, if the vehicle is equipped. This interface will maintain the data-controlled +12V accessory output as well as provide navigation outputs for reverse, vehicle speed pulse and parking brake. The FD02SR will also retain your four-inch factory display along with the clock adjustment and hazard/lock buttons. An interface is a small computer system that allows your new head unit to properly communicate with your vehicle's computer system. If you install a new aftermarket radio without using an interface, you will lose many of the standard security features of the vehicle. This is due to vehicle manufactures running part of the vehicle's computer system through the OEM radio. Functions lost include, but are not limited to, warning chimes (keys left in ignition, lights left on, low fuel etc.), security and alarm systems, +12V accessory and more.