Operation

OPERATION

Most 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 exception is the glove box lamp, which has a unique, dedicated 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 cargo/dome lamps located on the roof supports or in the headliner, the dome/reading lamps located in the optional Roof Control Module (RCM) (also known as the Overhead Control Panel/OCP control unit or DBE) in the headliner near the windshield and the entry/exit lamps located in the door step wells. Most lamps in the courtesy lamp circuit are provided with battery current and ground by the Body Control Module (BCM) (also known as the Signal Acquisition and Actuation Module/SAM). The battery current is provided directly by the BCM to all lamps. Ground to the front interior lamps is provided either through a take out of the vehicle wire harness secured to the body sheet metal or by the BCM directly. Ground to the rear interior lamps is provided by the BCM through the illumination relay.

The BCM monitors hard wired inputs from the door ajar switches and the optional interior rear lighting master switch or the optional interior rear lighting motion detector as well as electronic message inputs received over the Controller Area Network (CAN) data bus from the Electronic Ignition Switch/Central GateWay (EIS or EIS/CGW) (also known as the EZS control unit), the RCM (Vehicle Theft Security System/VTSS and Remote Keyless Entry/RKE system) and the Occupant Restraint Controller (ORC) (also known as the lowline or highline airbag control unit/ARCADE) (restraint system). The BCM uses these inputs along with internal programming to determine the proper outputs. The BCM then uses internal drivers to control the outputs to the appropriate interior lighting components. The BCM also 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 a pre-programmed interval.

PANEL LAMPS DIMMER CIRCUIT

The panel lamps dimmer circuit actually includes several modules and circuits. These modules and circuits control the illumination and dimming level of the instrument panel switch pod (also known as the Switch Bank Module/SBM or upper control panel/center console switch module/OBF control unit), the heater-air conditioner controls, as well as the back lighting for other switches and components in the instrument panel and the vehicle interior. All lamps in the panel lamps dimmer circuits are controlled by their respective electronic modules based upon electronic dimming level message inputs received from the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN or KOMBI) over the CAN data bus. These lamps are illuminated by a 12-volt Pulse Width Modulated (PWM) output of their respective module that synchronizes the illumination intensity of all lamps in the panel lamps dimmer circuits with that of the EMIC.

In addition, when the headlamps are turned OFF, all of the Organic Light Emitting Diode (OLED) display units or Liquid Crystal Display (LCD) units in the vehicle are illuminated at their full intensity levels for increased visibility when the vehicle is driven during daylight hours. When the headlamps are turned ON, the illumination intensity of these display units are also controlled by the electronic dimming level message inputs received by their modules from the EMIC.