Left Multi-Function Switch
LEFT MULTI-FUNCTION SWITCHDESCRIPTION
The left (lighting) multi-function switch is located on the left side of the steering column, just below the steering wheel. This switch is the primary control for the interior and exterior lighting systems. The only visible components of the switch are the control stalk (2), control knob (1) and control sleeve (3) that extend through the steering column shrouds on the left side of the column. The remainder of the switch including its mounting provisions, its electrical connection, and the turn signal cancel actuator are concealed beneath the shrouds.
The switch housing and controls are attached to the Steering Column Control Module (SCCM) (1) by one retaining screw. Each of the switch controls has white International Control and Display Symbol graphics applied to it, which clearly identify its many functions. A single integral interface connector connects the left multi-function switch directly to the SCCM (1).
The left multi-function switch provides the vehicle operator with a control interface for the following exterior lighting functions:
- Front Fog Lamps - For vehicles so equipped, the left multi-function switch control knob provides detent switching for the optional front fog lamps.
- Headlamps - The left multi-function switch control knob provides detent switching for the headlamps.
- Headlamp Beam Selection - The left multi-function switch control stalk provides detent switching for selection of the headlamp high or low beams.
- Headlamp Optical Horn - The left multi-function switch control stalk includes momentary switching of the headlamp high beam circuits to provide an optical horn feature (sometimes referred to as flash-to-pass), which allows the vehicle operator to momentarily flash the headlamp high beams as an optical signalling device.
- Park Lamps - The left multi-function switch control knob provides detent switching for the park lamps.
- Rear Fog Lamps - For vehicles so equipped, the left multi-function switch control knob provides detent switching for the optional rear fog lamps. Rear fog lamps are optional only for vehicles manufactured for certain markets, where they are required.
- Turn Signal Control - The left multi-function switch control stalk provides both momentary non-detent switching and detent switching with automatic cancellation for both the left and right turn signal lamps.
The left multi-function switch also provides the vehicle operator with a control interface for the following interior lighting functions:
- Interior Lamps Defeat - The left multi-function switch control ring provides detent switching to defeat the illumination of all interior courtesy lamps when a door, the rear flip-up glass, or the liftgate are opened.
- Interior Lamps On - The left multi-function switch control ring provides detent switching to simultaneously illuminate all interior courtesy lamps.
- Panel Lamps Dimming - The left multi-function switch control ring provides simultaneous adjustable control of the illumination intensity of all instrument panel lighting at one of six available illumination intensity levels.
- Parade Mode - The left multi-function switch control ring provides detent switching for a parade mode that maximizes the illumination intensity of all instrument panel lighting for visibility when driving in daylight with the exterior lamps turned on.
The left multi-function switch cannot be adjusted or repaired. If any function of the switch is damaged or inoperative, the entire switch unit must be replaced.
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:
- 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.