2002 cadi deville. master switches do not work (no control of any window), back two switches don't work. HELP

only the passenger front switch works. how can i check into this. is the door module at fault, is it only the master switches, or is it the electrical system. thanks for any tips.2002 cadi deville. master switches do not work (no control of any window), back two switches don't work. HELP
A lot of GM cars have broken the wires to the drivers side door in the flexable rubber boot that goes from the door to the pillar. I would pull the L/F window switch and see if the switch is sending the proper voltage to each window if it is OK at the switch then check the wiring from there to the pillar. These days though the body control computer has way too many uses and it may be the BCM or the wiring to it. You may have to invest in a book to get the wiring diagrams to show you what exactly happens when you ask your car for permission to open a window.