For 1990-2009 cars

The steering wheel controls consist of the following components:

• | The steering wheel radio control switches

• | The SIR coil assembly

• | The radio

### Steering Wheel Radio Control Switches

The steering wheel control switches control the following components:

• | The radio power

• | The volume

• | The station frequency

These switches are a ladder network consisting of these components:

• | The switches

• | A series of resistors

The ladder network is arranged so that each switch has a different resistance. The different resistances allow a different voltage output to the radio for each switch pressed.

### SIR Coil Assembly

The SIR coil assembly contains 4 wires. The wires are used by the steering wheel controls. The assembly allows voltages to be sent from the steering wheel switches to the radio while the steering wheel is being turned.