Interior Lighting - Operation

OPERATION

The lamps of the interior lighting system can be divided into two general classifications based upon the circuit that controls their operation: The courtesy lamp circuit (which includes the courtesy lamp load shed circuits for each lamp as well as the convenience circuits for those lamps with independent switching), or the panel lamps dimmer circuit. Following are paragraphs that briefly describe the operation of each of these interior lighting circuits.

The lamps and the hard wired circuits between components related to the interior lighting system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.

However, conventional diagnostic methods will not prove conclusive in the diagnosis of the interior lighting system or the electronic controls or communication between modules and other devices that provide some features of the interior lighting system. The most reliable, efficient, and accurate means to diagnose the interior lighting system or the electronic controls and communication related to interior lighting system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

COURTESY LAMP CIRCUIT

The courtesy lamp circuit includes the courtesy lamps located under each outboard end of the instrument panel, the dome or map/reading lamps located on the inner roof side rails adjacent to the front and second row outboard seating positions, the cargo or map/reading lamp located in the center of the headliner over the third row seating positions, the liftgate lamp located near the lower left corner of the liftgate trim panel, the glove box lamp in the top of the glove box opening in the instrument panel, and the vanity lamps located in the sun visors.

The lamps in the courtesy lamp circuit are provided with battery voltage and ground by the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) using internal drivers through a courtesy lamp driver circuit and ground circuits based upon hard wired inputs from the rear door ajar switches, the flip-up glass ajar switch, and the liftgate ajar switch as well as electronic front door ajar switch status message inputs received from the from the Driver Door Module (DDM) and the Passenger Door Module (PDM). The EMIC also uses electronic left multi-function switch message inputs received from the Steering Control Module (SCM) over the Local Interface Network (LIN) data bus and ignition switch status received from the Wireless Ignition Node (WIN) over the Controller Area Network (CAN) data bus.

After all of the ajar switch inputs to the EMIC transition to open, the EMIC will keep the courtesy lamps illuminated for about 30 seconds, then fade the lamps to OFF (theater dimming) over about 3 seconds. The EMIC also provides courtesy lamp operation based upon the electronic left multi-function switch status messages received from the SCM, and provides an illuminated entry feature in response to certain electronic message inputs received from the WIN and the Occupant Restraint Controller (ORC) over the CAN data bus. A courtesy lamp DEFEAT mode based upon an electronic left multi-function switch status message received from the SCM will cause the EMIC to override normal courtesy lamp operation based upon any ajar switch inputs.

For those lamps on the courtesy lamp circuit with independent switching, such as the standard or optional map/reading lamps, the vanity lamps and the glove box lamp the EMIC provides a ground path to the switches using another internal driver through a separate courtesy lamp load shed circuit. The EMIC provides a battery saver (load shedding) feature for all courtesy lamps, which will automatically turn these lamps OFF if they are left ON for more than about eight minutes with the ignition switch in the OFF position.

PANEL LAMPS DIMMER CIRCUIT

The panel lamps dimmer circuit actually includes several circuits. These circuits control the illumination and dimming level of the upper and lower instrument panel switch pods, the front and rear heater-air conditioner controls, the four-wheel drive selector switch and the transmission gearshift lever assembly. All lamps in the panel lamps dimmer circuits are provided a path to ground at all times through a hard wired ground circuit. These lamps are illuminated by a 12-volt Pulse Width Modulated (PWM) output of the EMIC through the panel lamps dimmer circuits.

This shared PWM output synchronizes the selected illumination intensity level of all of the lamps in the panel lamps dimmer circuits. The EMIC uses electronic left multi-function switch status and dimming level message inputs received from the SCM over the LIN data bus. The SCM sends the proper left multi-function switch status and dimming level messages based upon the exterior lighting selection of the control knob and the dimming level selection of the control sleeve on the left multi-function switch control stalk.

The EMIC, the instrument panel switch pods and the radio use the dimming level messages from the SCM to control the illumination intensity of their own back lighting and controls. In addition, when the control sleeve of the left multi-function switch is moved to the PARADE (or funeral) mode detent position, all of the Vacuum Fluorescent Display (VFD) units in the vehicle are illuminated at their full intensity levels for increased visibility when the vehicle is driven during daylight hours with the exterior lights turned ON. The PARADE mode has no effect on the illumination intensity of incandescent panel lamps.