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 and, depending upon the selected vehicle options may include either the front dome lamp located on the headliner between the sun visors near the windshield header or the map/reading lamps located in the mini overhead console near the windshield header, the second row dome lamp located in the headliner near the center between the second row seat back and the cargo area, 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 two ground circuits based upon electronic ajar switch status message inputs received from the Totally Integrated Power Module (TIPM) over the Controller Area Network (CAN) data bus. The EMIC also uses electronic left multi-function switch and ignition switch status message inputs received from the Steering Control Module (SCM) over the Local Interface Network (LIN) data bus to control these outputs.

After all of the ajar switch inputs to the TIPM 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 Sentry Key REmote Entry Module (SKREEM) (also known as the Wireless Control Module/WCM) 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 to the TIPM.

For those lamps on the courtesy lamp circuit with independent switching such as the front dome lamp, the optional reading lamps and the vanity lamps, the EMIC provides a second battery feed to the switches using another internal driver through a separate courtesy lamp load shed circuit (also known as the convenience 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 heater-air conditioner controls and the automatic transmission gear selector bezel lamp. 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 circuit.

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 pod 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.