Interior Lighting - Operation

OPERATION

The lamps of the interior lighting system can be divided into general classifications based upon the circuit that controls their operation: The courtesy lamp circuit, the reading lamps circuit and the panel lamps dimmer circuit. The standard 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 the courtesy lamps, reading lamps and panel lamps dimmer 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 dome or map and reading lamps located in the overhead console near the windshield and in the headliner over the second and optional third row seating positions, the liftgate lamps located near each lower 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 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 dimmer module and electronic message inputs from the ignition switch (also known as the Wireless Ignition Node/WIN) and the Totally Integrated Power Module (TIPM).

After all of the ajar switch inputs to the TIPM transition to open and the EMIC receives the appropriate electronic ajar switch status messages from the TIPM over the Controller Area Network (CAN) data bus, 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 interior lighting thumbwheel of the dimmer module, and provides an Illuminated Entry feature in response to certain electronic ignition switch status message inputs received from the WIN and the Occupant Restraint Controller (ORC) over the CAN data bus. A courtesy lamp DEFEAT mode input based upon a resistor multiplexed input from the interior lighting thumbwheel of the dimmer module will cause the EMIC to override normal courtesy lamp operation.

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 after the electronic ignition switch status message transitions to OFF. If any courtesy lamp input is received subsequent to a 10 minute load shed and prior to a new ignition cycle, the courtesy lamps will turn OFF after 90 seconds.

READING LAMP CIRCUIT

For those lamps on the courtesy lamp circuit with independent switching such as the reading lamps, the optional vanity lamps and the glove box lamp, the EMIC also provides a battery voltage output to those switches through a separate reading lamp circuit. The EMIC provides a battery saver (load shedding) feature for the reading lamp circuit as well as the courtesy lamp circuit, which will automatically turn these lamps OFF if they are left ON for more than about 10 minutes after the electronic ignition switch status message transitions to OFF. If any reading lamp input is received subsequent to a 10 minute load shed and prior to a new ignition cycle, the reading lamps will turn OFF after 90 seconds.

PANEL LAMPS DIMMER CIRCUIT

The panel lamps dimmer circuit actually includes several circuits. These circuits control the back lighting illumination and dimming level of the headlamp switch, the dimmer module, the heater-air conditioner controls, the instrument panel switch pod, the four-wheel drive selector switch, the automatic transmission gear selector bezel lamp, the front door map pocket and remote inside handle lamps, as well as the center floor console cup holder and forward storage compartment lamps. 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 several panel lamps dimmer circuits.

This shared PWM output synchronizes the selected illumination intensity level of all the lamps in the panel lamps dimmer circuits. The EMIC uses hard wired resistor multiplexed inputs from the rotary exterior lighting control knob of the headlamp switch to determine when the exterior lighting is turned ON and from the thumbwheel of the dimmer module to determine the dimming level selection. Then the EMIC provides the appropriate PWM outputs through the panel lamps dimmer circuits as well as electronic dimming level messages over the CAN data bus to other electronic modules in the vehicle.

The EMIC, the instrument panel switch pod and the radio use the electronic dimming level messages to control the illumination intensity of their own back lighting, controls and display units. In addition, when the interior lighting thumbwheel of the dimmer module is moved to the PARADE (or funeral) mode detent position, all of the electronic display units are illuminated at their full intensity levels for increased visibility when the vehicle is driven during daylight hours with the exterior lighting turned ON. The PARADE mode has no effect on the illumination intensity of incandescent panel lamps.