Change duty cycle, inspect a simplified scope trace, and diagnose an electronically controlled lamp.
A body control module can control lamp power by rapidly switching an output ON and OFF. Duty cycle is the percentage of each switching period spent ON. In this simplified resistive-lamp model, increasing duty cycle increases average applied voltage and average power. Real LED drivers and BCMs can behave differently.
This lab uses a simplified high-side switched lamp circuit. The scope probe measures the lamp's positive terminal relative to battery negative.
Switch OFF. Command is disabled.
A conventional DC voltmeter may display an average or another processed value on a PWM signal. A scope shows the switching waveform; measurement behavior depends on the instrument.
A lamp is commanded ON at 50% duty. The scope at the lamp feed shows a steady 0 V, while battery voltage is present at the BCM supply. Which fault in this teaching circuit is most consistent with the observation?
Use the waveform and circuit conditions to reason through the fault.
Training-only, idealized 12.6 V high-side PWM model. It does not model thermal response, LED constant-current drivers, module protection, multiplexing or OEM-specific wiring. Always follow vehicle service information for real diagnostics.