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Home >> Saab >> 2011 >> 9-5 Turbo6 >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Headlights >> Lighting And Signaling Systems >> Fault diagnosis, symptoms >> Interior Backlighting Malfunction >> Circuit/System Description

Circuit/System Description

The body control module (BCM) supplies a reference voltage to the backlight dimmer switch, which is part of the headlamp switch. When the backlight dimmer switch is placed in a desired brightness position, reference voltage is applied through the backlight dimmer switch resistor ladder to the BCM. The BCM interprets this voltage signal, then applies a pulse width modulated (PWM) voltage to the LED dimming supply circuit to all related interior lamps, illuminating them to the desired level of brightness.