Operation

OPERATION

The left (lighting) multi-function switch uses resistor multiplexing to control the many functions and features it provides using a minimal number of hard wired circuits. The switch then sends electronic switch status messages over the Local Interconnect Network (LIN) to the Cab Compartment Node (CCN) and then the CCN sends messages over the Controller Area Network (CAN) data bus to the Totally Integrated Power Module (TIPM) other electronic modules in the vehicle.

For lighting and wiper function it sends the messages over the LIN bus to the CCN and the CCN puts them out on the CAN bus to the other modules. The left switch has the microprocessor for all communication to the TIPM. The SCCM is composed of a clockspring and left lighting switch and a right wiper switch. The TIPM, controls the lighting and wiper functions.

The left multi-function switch can be diagnosed using LIN based diagnostic tools and methods. However, the most reliable, efficient and accurate means to diagnose this component requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

EXTERIOR LIGHTING

Following are descriptions of how the left multi-function switch is operated to control the many exterior lighting functions and features it provides:

- Auto Headlamps - The optional automatic headlamps feature is requested when the left multi-function switch control knob is rotated to the automatic (A) detent position with the ignition switch in the ON position. The SCM reads the resistor multiplexed input from the left multi-function switch and sends an electronic switch status message over the CAN data bus to the other electronic modules in the vehicle.
- Front Fog Lamps - The optional front fog lamps are requested when the left multi-function switch control knob is pulled outward to the front fog lamps detent position. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle. The switch control knob incorporates an internal cam mechanism that will only allow the front fog lamps to be selected while the headlamp On position is also selected, and will automatically move the control knob to the front fog lamps Off position when the control knob is rotated to deselect the headlamps.
- Headlamps - The headlamps are requested when the left multi-function switch control knob is rotated to the headlamps on detent position. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle.
- Headlamp Beam Selection - The headlamp beams are selected when the left multi-function switch control stalk is pushed forward. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle. Each time the control stalk is actuated in this manner, the headlamp beams are toggled from the current selection to the opposite selection.
- Headlamp Optical Horn - The headlamp optical horn is selected each time the left multi-function switch control stalk is pulled rearward to a momentary position just short of the beam selection detent position. The headlamp high beams will remain illuminated for as long as the control stalk is held in this momentary position and the previously selected beams will be restored when the control stalk is released. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle.
- Park Lamps - The headlamps are requested when the left multi-function switch control knob is rotated to the park lamps on detent position. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle.
- Rear Fog Lamps - The optional rear fog lamps are requested when the left multi-function switch control knob is pulled outward to the front fog lamps detent position and then rotated to the rear fog lamps detent position. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle. The switch control knob incorporates an internal cam mechanism that will only allow the rear fog lamps to be selected while the front fog lamps On position is also selected, and will automatically move the control knob to the rear fog lamp Off position when the control knob is pushed in to deselect the front fog lamps.
- Turn Signal Control - The turn signals are requested when the left multi-function 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 "lane change" position in each direction that provides turn signals only until the control stalk is released. When the control stalk is moved to a detent turn signal switch position, a 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 left 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. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle.

INTERIOR LIGHTING

Following are descriptions of the how the left multi-function switch is operated to control the many interior lighting functions and features it provides:

- Interior Lamps Defeat - The interior lamps defeat feature is requested when the left multi-function switch control sleeve is rotated to the interior lamps defeat detent position. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle.
- Interior Lamps On - The interior lamps on feature is requested when the left multi-function switch control sleeve is rotated to the interior lamps On detent position. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle.
- Panel Lamps Dimming - The panel lamps dimming function is active only when the left multi-function switch control knob is in any exterior lighting On position. With the exterior lighting On, the panel lamps dimming level is requested when the left multi-function switch control sleeve is rotated to any one of five minor detent positions. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle.
- Parade Mode - The parade or funeral mode is active only when the left multi-function switch control knob is in any exterior lighting On position. With the exterior lighting On, the parade mode is requested when the left multi-function switch control sleeve is rotated to the parade mode detent position. The left multi-function switch sends an electronic switch status message over the LIN bus to the CCN, then over the CAN data bus to the other electronic modules in the vehicle.