Keyless Entry Interior Illumination
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
Power comes from the dome fuse, through the Left Instrument Panel Junction Block and finally to the dome lamp. When the transmitter activates the keyless entry system it causes the multifunction alarm module to provide ground to the dome lamp, and the lamp will illuminate.