Output Switching Modules
WARNING: This page is about a different car, the 1988 Cadillac Allante and 1987 Cadillac Allante. However, it is still accessible from the selected car via links, so may be relevant.
Each Output Switching Module (OSM) is a solid state device consisting of 4 inputs to the power lamps, address pins identifying the location of the OSM, 2 data circuits to communicate with the BCM, a power circuit and a ground circuit. See Fig 1.
The OSM depends on the commands received from the BCM to turn on or off its outputs resulting in operation of all the various lamps in the lighting system as needed. These consist of the headlamps, taillamps, turn signal lamps or courtesy lamps.