Instrument Panel Dimming
WARNING: This page is about a different car, the 2002 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
I/P dimming is accomplished using the BCM. The panel dimming level switch is read by the BCM, which converts the level to a value that is sent over the PCI bus. Other modules such as the Radio, MIC, and the EVIC use this data so their display intensity matches the other incandescent bulbs in the vehicle that are driven directly by the BCM.