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, or the panel lamps dimmer circuit. The optional center bezel lamp is actually controlled by a park lamps output of the Totally Integrated Power Module (TIPM), which energizes this circuit at a fixed intensity whenever the exterior lighting is illuminated. 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

Depending upon the selected vehicle options the courtesy lamp circuit may include the dome and dome/reading lamps located in the headliner near the windshield, between the front and rear seating, the cargo lamps located near the center of the rear roof header, 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 a path to ground at all times. The ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) controls the output of battery voltage for the courtesy lamps in this circuit based upon hard wired inputs from the door ajar switches, the headlamp switch and the ignition switch.

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 a resistor multiplexed input from the vertical thumbwheel on the headlamp switch, and provides an illuminated entry feature in response to certain electronic message inputs received from the Sentry Key REmote Entry Module (SKREEM) (also known as the Wireless Control Module/WCM) and the Occupant Restraint Controller (ORC) over the Controller Area Network (CAN) data bus. A resistor multiplexed courtesy lamp DEFEAT input from the vertical thumbwheel of the headlamp switch will cause the EMIC to override normal courtesy lamp operation based upon inputs from all of the ajar switches.

For those lamps on the courtesy lamp circuit with independent switching such as the standard or optional map/reading lamps, the optional vanity lamps, and the glove box lamp the EMIC provides a battery voltage output to the switches through a separate 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 10 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 headlamp switch, the heater-air conditioner controls and the four-wheel drive selector switch. 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 illuminate based upon inputs to the EMIC from the rotary control knob and vertical thumbwheel of the headlamp switch. The control knob on the headlamp switch selects the exterior lights, while the thumbwheel selects the panel lamps intensity (dimming) level.

When the exterior lighting is turned ON, the EMIC provides electronic dimming level messages to the radio and the Compass Mini-Trip Computer (CMTC) or Electronic Vehicle Information Center (EVIC) over the CAN data bus. The EMIC also supplies a 12-volt Pulse Width Modulated (PWM) output to all of the incandescent lamps through several panel lamps dimmer circuits. This shared PWM output synchronizes the selected illumination intensity level of all of the lamps in the panel lamps dimmer circuit.

The radio and the CMTC or EVIC each use the dimming level messages to control the illumination intensity of both their Vacuum Fluorescent Display (VFD) units and their control lighting. In addition, when the thumbwheel of the headlamp switch is moved to the PARADE (or funeral) mode detent position, all of the VFD units 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.