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Operation







OPERATION

The multi-function switch (also known as the combination switch) uses resistor multiplexing to control the many functions and features it provides using only limited hard wired output circuits. The switch receives a clean ground from the clockspring/Steering Control Module (SCM) (also known as the steering column module/MRM), then provides return outputs to the SCM to control all headlamp beam selection, turn signal, washer and wiper functions. The SCM converts the multi-function switch inputs to electronic switch status messages, which are transmitted to other electronic modules in the vehicle over the Controller Area Network (CAN) data bus.

The multi-function switch operates as follows:

- Headlamp Beam Selection - The control stalk of the multi-function switch is pushed towards the instrument panel past a detent to actuate the integral high beam select switch circuitry, or pulled past the detent toward the steering wheel to actuate the low beam select switch circuitry. Pulling the control stalk toward the steering wheel to a momentary position from the low beam selection actuates the optical horn (also known as headlamp flasher feature. Each time the control stalk is actuated to a detent position, the opposite headlamp beam from what is currently selected will be energized. Each time the control stalk is actuated to the momentary position with the headlamps turned OFF, the headlamp high beams will be illuminated for as long as the control stalk is held in this position. The multi-function switch provides an output to the SCM, and the SCM responds by sending electronic beam select switch status messages to the Body Control Module (BCM) (also known as the Signal Acquisition and Actuation Module/SAM) over the CAN data bus. The BCM energizes or de-energizes the selected LOW or HIGH beam circuits.
- Turn Signal Control - The control stalk of the multi-function switch is moved upward to activate the RIGHT turn signal circuitry, and, downward to activate the LEFT turn signal circuitry. The turn signal switch has a detent position in each direction that provides turn signals with automatic cancellation, and an intermediate, momentary position in each direction that automatically provides three turn signal blinks as a LANE CHANGE feature when the control stalk is tapped, or will energize the turn signals for as long as the control stalk is held in the momentary position. When the control stalk is moved to a detent turn signal switch position, the cancel actuator extends toward the center of the steering column. A turn signal cancel cam that is integral to the clockspring rotates with the steering wheel and the cam lobes contact the cancel actuator when it is extended from the multi-function switch. When the steering wheel is rotated during a turning maneuver, one of the two turn signal cancel cam lobes will contact the turn signal cancel actuator. The cancel actuator latches against the cancel cam rotation in the direction opposite that which is signaled. If the LEFT turn signal detent is selected, the lobes of the cancel cam will ratchet past the cancel actuator when the steering wheel is rotated to the left, but will unlatch the cancel actuator as the steering wheel rotates to the right and returns to center, which will cancel the turn signal event and release the control stalk from the detent so it returns to the neutral OFF position. When a turn signal is activated, the multi-function switch provides an output to the SCM, and the SCM responds by sending electronic turn signal switch status messages to the BCM over the CAN data bus. The BCM energizes and flashes or de-energizes the selected left or right turn signal circuits.
- Washer Control - The control knob on the end of the multi-function switch control stalk is depressed towards the steering column to an actuation point to activate the front wiper system for a single wipe cycle, or past the actuation point to actuate the front washer pump. The front washer pump will continue to operate in the washer mode for as long as the control knob is held depressed. The multi-function switch provides an output to the SCM, and the SCM responds by sending electronic front washer switch status messages to the BCM over the CAN data bus. The BCM responds by energizing or de-energizing the front wiper motor or front washer pump. If the vehicle is so equipped, the control sleeve on the multi-function switch control stalk is rotated up or down to the momentary rear wash position to activate the rear washer pump. The rear washer pump will continue to operate in the rear washer mode for as long as the control sleeve is held in the momentary rear wash position. The multi-function switch provides an output to the SCM, and the SCM responds by sending electronic rear washer switch status messages to the BCM over the CAN data bus. The BCM responds by energizing or de-energizing the rear washer pump.
- Wiper Control - The control knob on the end of the multi-function switch control stalk is rotated to one of the three front wiper detents, or to the OFF position to select the front wiper mode. The multi-function switch provides an output to the SCM, and the SCM responds by sending electronic front wiper switch status messages to the BCM over the CAN data bus. The BCM responds by energizing or de-energizing the front wiper motor. The BCM is programmed to operate the front wiper motor at the selected low, high or intermittent wipe speed. If the vehicle is so equipped, rotating the control sleeve on the multi-function switch control stalk to the detent rear wiper position actuates the rear wiper motor. The multi-function switch provides an output to the SCM, and the SCM responds by sending electronic rear wiper switch status messages to the BCM over the CAN data bus. The BCM responds by energizing or de-energizing the rear wiper relay in the rear wiper motor.

The hard wired circuits of the multi-function switch may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the multi-function switch or the electronic controls or communication between modules and other devices that provide some features of the multi-function switch. The most reliable, efficient, and accurate means to diagnose the multi-function switch or the electronic controls and communication related to multi-function switch operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.