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 up or down, the switch completes a ground circuit to provide input to the SCCM  corresponding to the desired action. The SCCM  sends a message to the BCM  over the HS-CAN  to communicate the dimmer switch input. Based on this message from the SCCM  , the BCM  determines the proper dimming level and 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 from the BCM  or the data received is deemed invalid for 5 seconds or less, the module will default the illumination to the last received setting. If a receiving module does not receive the illumination dimming level message or the data received is deemed invalid for more than 5 seconds, the module sets a DTC in continuous memory and defaults the illumination to full nighttime intensity.

The BCM  also sends a pulse width modulated voltage to the hard-wired dimmable switches. Refer to the SYSTEM DIAGRAM  to view the networked and hard-wired illumination sources.