Dimmable Backlighting

The dimmable switches and components are illuminated when the parking lamps are on. The instrument panel dimmer switch controls all dimmable interior illuminated components. On vehicles equipped with autolamps, if the exterior lamps are activated during the daytime, the message center illumination remains at full intensity and does not dim from the instrument panel dimmer switch during this condition. If the vehicle travels under a bridge or a tunnel, the low level of ambient light causes the illumination level of the message center to change to the level set by the instrument panel dimmer switch. The message center illumination changes back to full intensity when the intense ambient light is restored.

When the parking lamps are on, the SCCM monitors the input from the instrument panel dimmer switch. When the dimmer switch is pressed, it provides input to the SCCM by completing a ground circuit corresponding to the desired action (increase backlighting intensity, decrease backlighting intensity or courtesy lamp on/defeat). The SCCM sends a message to the BCM over the HS-CAN to relay the dimmer switch input. Based on this message, the BCM sends a pulse-width modulated voltage to the hard-wired dimmable switches.

The BCM also sends an illumination dimming level message over the HS-CAN and MS-CAN to command the illumination dimming level of networked modules. This message is gatewayed to the I-CAN by the IPC.

If a receiving module does not receive the illumination dimming level message or the data received is deemed invalid for 5 seconds or less, the receiving module defaults the backlighting to the last setting. If the receiving module does not receive the illumination dimming level message or the data received is deemed invalid for more than 5 seconds, the receiving module sets a DTC in continuous memory and defaults the backlighting to full nighttime intensity.