Rear Window Defogger
WARNING: This page is about a different car, the 2005 Dodge Stratus and 2005 Chrysler Sebring. However, it is still accessible from the selected car via links, so may be relevant.
The Body Control Module (BCM) controls the operation of the Rear Defogger Relay located in the Junction Block. The BCM will energize the relay when it receives a request from the HVAC control head (PCI bus message for Automatic Temperature Control or a MUX input for Manual Temp Control). With the relay activated, it will supply battery voltage to the rear window defogger grid along with heat mirrors if so equipped.