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<\/a><\/p>\nFig. 1<\/strong><\/p>\n <\/p>\n Exterior and Interior Lighting is the fifth topic in the TechLink series highlighting several of the related systems handled by the Body Control Module (BCM) on GM models built with the Vehicle Intelligence Platform (VIP). The goal of this series is to help improve understanding of the components operated by the BCM and reduce warranty claims and unnecessary component replacement.<\/p>\n The earlier systems in the series are Keyless Entry System<\/strong><\/a>, Content Theft Deterrent<\/a>,<\/strong> Door Latch Actuators<\/a>,<\/strong> and Tire Pressure Monitoring Systems<\/strong><\/a>.<\/p>\n COMPONENT BREAKDOWN<\/strong><\/p>\n LIGHTING SYSTEMS OVERVIEW<\/strong><\/p>\n The exterior and interior lighting systems operate using serial-data communication, LIN and private CAN networks, pulse-width-modulated (PWM) outputs, feedback circuits, and timed battery-protection strategies, all of which contribute to what the customer sees as a simple light turning on or off.<\/p>\n Exterior Lighting<\/strong><\/p>\n The complexity of modern lighting systems is illustrated by the variety of functions performed by the exterior lighting (Fig. 2), such as automatic headlamps and Daytime Running Lamps, IntelliBeam, headlamp leveling, turn-signal animation, tail lamp communication, stop lamp illumination during regenerative braking, approach and exit lighting, grille and emblem illumination, and charge-port lighting. One example is the K26 Headlamp Control Module. As a key part of the forward-lighting architecture, it receives suspension position information and controls headlamp leveling actuators to maintain the intended aim as the vehicle moves.<\/p>\n Fig. 2<\/strong><\/p>\n <\/p>\n Interior Lighting<\/strong><\/p>\n Interior lighting (Fig. 3) adds another layer of complexity with features including dome and courtesy lamps, reading and compartment lamps, door-sill illumination, dimmable backlighting, and LIN-controlled ambient lamps whose color and intensity can change based on user settings and vehicle events.<\/p>\n Fig. 3<\/strong><\/p>\n <\/p>\n System Operation<\/strong><\/p>\n In both exterior and interior lighting systems, a customer-visible symptom may originate from an input, a module command, a power or ground circuit, a sensor, a communication network, a feedback circuit, or the lamp assembly itself.<\/p>\n For this reason, effective lighting diagnosis begins with understanding the intended system operation. Before replacing a lamp or control module, verify the conditions that should create the command, confirm the relevant module response, and check power, ground, communication, feedback, sensor, and output circuits in the correct sequence. When the concern involves beam aim or leveling, include the K26 Headlamp Control Module, front and rear suspension position sensors, dedicated communication circuits, and headlamp actuators in the diagnostic path. Also keep in mind that some behaviors are designed responses: e.g., interior or exterior lamps that turn off after approximately 10 minutes may be operating normally under battery-rundown protection. A system-level diagnostic approach can prevent unnecessary parts replacement, reduce repeat repairs, and help resolve lighting-related warranty concerns more accurately.<\/p>\n EXTERIOR LIGHTING ARCHITECTURES<\/strong><\/p>\n Here are a few examples of exterior forward-lighting architectures showing the display and switch inputs, K9 BCM coordination, K219 Lighting Control Module outputs, K26 headlamp aiming and adaptive functions, and headlamp feedback and control paths. (Fig. 4; Typical headlamp system with Headlamp Leveling), (Fig. 5; Typical exterior forward lighting system) and (Fig. 6, Typical headlamp system)<\/p>\n <\/p>\n Fig. 4 – Typical headlamp system with Headlamp Leveling, RPO TR7, on 2024 and later model year VIP vehicles<\/strong><\/p>\n <\/p>\n\n
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