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 ambient (halo) lamp circuit, the courtesy lamp circuit, the reading lamps circuit and the panel lamps dimmer circuit. Following are paragraphs that briefly describe the operation of each of the ambient lamps, 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.

AMBIENT (HALO) LAMP CIRCUIT

The ambient (halo) lamps circuit includes each of the halo lamps located strategically to aid visibility within the vehicle interior while driving at night. The lamps in the ambient 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 ambient lamps in this circuit based upon hard wired inputs from the headlamp switch and electronic message inputs from the ignition switch (also known as the Wireless Ignition Node/WIN) and the Totally Integrated Power Module (TIPM).

The EMIC provides dimmable lighting level ambient lamp operation based upon a resistor multiplexed input from the ambient (halo) lighting thumbwheel on the dimmer module (Left-Hand Drive/LHD), or fixed lighting level ambient lamp operation based upon a resistor multiplexed input from the ambient (halo) lighting push button of the headlamp switch (Right-Hand Drive/RHD).

COURTESY LAMP CIRCUIT

The courtesy lamp circuit includes the courtesy lamps below 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 headliner or the overhead consoles near the windshield and between the second and third row seating, the liftgate lamp located near the center of the liftgate trim 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 headlamp switch 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 on the dimmer module (Left-Hand Drive/LHD) or the interior lighting thumbwheel of the headlamp switch (Right-Hand Drive/RHD), and provides an Illuminated Entry feature in response to certain electronic ignition switch status message inputs received from the Wireless Ignition Node (WIN) and the Occupant Restraint Controller (ORC) over the CAN data bus. A resistor multiplexed courtesy lamp DEFEAT input from the interior lighting thumbwheel of the dimmer module (LHD) or the headlamp switch (RHD) 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 and the optional vanity lamps, 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 (LHD), the gear selector indicator (RHD), the instrument panel switch pod, the front and rear heater-air conditioner controls, the map pocket lamps, as well as the instrument panel cup holder 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 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 inputs from the rotary exterior lighting control knob of the headlamp switch and the interior lighting thumbwheel of the dimmer module (LHD) or the headlamp switch (RHD) to determine when the exterior lighting is turned ON and 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 (LHD) or the headlamp switch (RHD) 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.