System Communication
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.
The communication between the 9 OSM modules, the BCM and the Left Switch Pod (LSP) is the duty of the data line circuits. The BCM continuously scans from the LSP to each of the 9 OSM modules, one at a time. As it is doing this, it is continuously making commands and requesting information from each component. See Fig 1.
The data line circuit is designed as a complete loop so that each element on the data line circuit has 2 data inputs. This loop design allows the circuit to work with one open in the circuit.