For 1990-2009 cars

The steering wheel radio control switch remotely controls various functions of the radio. The steering wheel radio control switch is a ladder network consisting of switches and resistors. The network is arranged so that each switch has a different resistance value. When a switch is pressed, a different voltage is input into terminal F8 of the radio. The radio then responds accordingly. When the park lamps are turned ON, terminal F3 of the radio outputs a voltage to turn ON the steering wheel control switch lamps. Terminal D of the steering wheel controls connector and terminal F9 of the radio connector are permanently grounded to G201.