For 1990-2009 cars

The steering wheel control switches duplicate the function of the primary controls of the associated component, through a network of multiple momentary contact switches and a series of resistors. The steering column control module (SCCM) supplies voltage to the switches and monitors the return signal for when a switch is pressed, a specific voltage drop occurs. The SCCM identifies the one selected, then sends a serial data message that is received by the component controlled, activating the feature.

This section is intended to diagnosis the circuits between the SCCM and the steering wheel control switches. If the primary control for the device is inoperative, refer to the appropriate section for the component the steering wheel control switch is controlling.