Steering Column Control Module (SCCM)

The multifunction switch uses resistor multiplexing to control the many functions and features it provides using a minimal number of hard wired circuits. The switch receives clean grounds from the SCCM, then provides resistor multiplexed return outputs to the SCCM to indicate the selected switch positions. The SCCM then sends electronic switch status  messages over the CAN data bus to the BCM and other electronic modules in the vehicle.

If the SCCM detects no inputs from the multifunction switch, it transmits an electronic Signal Not Available (SNA)  status message over the CAN data bus. The SNA status signals the other electronic modules to implement a fail-safe or default mode of operation. For the exterior lighting system, the multifunction switch fail-safe mode automatically selects LOW beams when the headlamps are turned ON. For the wiper system, the multifunction switch fail-safe mode will maintain the last selected wiper system mode of operation for the remainder of the current ignition cycle, after which the wiper system will default to OFF.

Following are descriptions of how the multifunction switch is operated to control the functions and features it provides:

• Headlamp Beam Selection  - The headlamp high beams are selected when the multifunction switch control stalk is pushed forward to the high beam selection detent position. The low beams are selected when the control stalk is pulled rearward to the low beam selection detent position. The SCCM reads the input from the multifunction switch and sends an electronic beam select switch status  message over the CAN data bus to the BCM and to other electronic modules in the vehicle.
• Headlamp Optical Horn  - The headlamp optical horn is selected each time the multifunction switch control stalk is pulled fully rearward to a momentary position. The headlamp HIGH beams will remain illuminated for as long as the control stalk is held in this momentary position and the LOW beams will be restored when the control stalk is released. The SCCM reads the resistor multiplexed input from the multifunction switch and sends an electronic beam select switch status  message over the CAN data bus to the BCM and to other electronic modules in the vehicle.
• Turn Signal Control  - The turn signals are requested when the multifunction switch control stalk is moved downward (LEFT signal) or upward (RIGHT signal). The control stalk 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, a cancel actuator extends from the multifunction switch through the SCCM mounting housing toward the center of the steering column. A turn signal cancel cam that is integral to the clockspring rotor rotates with the steering wheel and the cam lobes contact the cancel actuator when it is extended from the multifunction switch. When the steering wheel is rotated during a turning maneuver, one of the 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. The SCCM reads the resistor multiplexed input from the multifunction switch and sends an electronic turn signal switch status  message over the CAN data bus to the BCM and to other electronic modules in the vehicle.

Inputs

• Left stalk turn requests

Outputs

• Optical Horn request to the BCM
• High beam state to the BCM
• Turn signal lever state to the BCM