Rear Window Operation
WARNING: This page is about a different car, the 2009 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
The DDM and FPDM supply their respective rear power window switches with a 12-volt reference and signal circuit. The rear power window switches contain separate resistors for each switch position. When a rear power window switch is activated, the associated door control module interprets the signal and checks for messages from other vehicle control modules prohibiting the window movement.
If no prohibitive messages have been received, the door control module sends a LIN serial data message to the appropriate power window motor commanding the requested window position.