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 body control module (BCM) supplies voltage to the switches and monitors the return signal. When a switch is pressed, a specific voltage drop across the resistors. The BCM identifies the switch selected, sends a serial data message to the component controlled by the switch and activates the feature.

This section is intended to diagnosis the circuits between the BCM 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 used for.