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. In vehicles equipped with the optional ambient lighting package, the ambient lights are actually controlled by the courtesy lamp circuit as well as by dedicated ambient lighting outputs based upon an input from the ambient lighting thumbwheel of the dimmer module. 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

Depending upon the selected vehicle options, the courtesy lamp circuit may include either the dome or map and reading lamps located in the overhead console near the windshield, the map and reading lamp integral to the grab handle above each rear door opening, the trunk lamp located in the left trunk 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 Body Control Module (BCM) (also known as the Common Body Controller/CBC) 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 Keyless Ignition Node/KIN) and the Radio Frequency (RF) Hub.

After all of the ajar switch inputs to the BCM transition to open, the BCM will keep the courtesy lamps illuminated for about 30 seconds, then fade the lamps to OFF (theater dimming) over about 3 seconds. The BCM 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 KIN, the RF Hub 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 thumbwheel will cause the BCM to override normal courtesy lamp operation.

The BCM 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.

AMBIENT LIGHTING

Vehicles equipped with the ambient lighting option have a second, dedicated ambient lighting thumbwheel located in the dimmer module. This thumbwheel controls the Light Emitting Diode (LED) units in the inside door latch release handle pockets and the door map pockets. The ambient lighting can be turned ON at full brightness or OFF using the ambient lighting thumbwheel. When the exterior lighting is turned ON, the ambient lighting can be dimmed using the ambient lighting thumbwheel. The ambient lighting is also controlled by the courtesy lamp circuit and will be turned ON at full brightness whenever the other courtesy lamps are turned ON, regardless of the ambient lighting thumbwheel setting.

The ambient lighting thumbwheel provides a resistor multiplexed input to the BCM. The BCM controls the front door ambient lighting using electronic messages sent to the door modules (also known as the Driver Door Module/DDM and Passenger Door Module/PDM) over the CAN data bus. The door modules then regulate the voltage output to the front door ambient lighting LED units accordingly. The BCM provides direct hard wired outputs to control the rear door ambient lighting LED units.

READING LAMP CIRCUIT

For those lamps on the courtesy lamp circuit with independent switching such as the map and reading lamps, the optional vanity lamps and the glove box lamp, the BCM also provides a battery voltage output to those switches through a separate reading lamp circuit. The BCM 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 courtesy 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 automatic transmission gear selector bezel lamp as well as the center floor console cup holder 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 BCM or the door control modules (also known as the Driver Door Module/DDM or Passenger Door Module/PDM) 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 BCM 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 BCM 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 Instrument Cluster (IC) (also known as the Common Instrument Cluster/CIC) and the Integrated Center Stack (ICS) 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.