Fault Detection: Notes
WARNING: This page is about a different car, the 1989 Cadillac Allante. However, it is still accessible from the selected car via links, so may be relevant.
As the BCM scans each OSM and the switch pod. It makes both commands and requests of each element. The information requested from each OSM informs the BCM about the integrity of each of the four outputs of the OSM. Therefore, if an OSM detects an open or short on one of its outputs, it informs the BCM of this problem. The BCM in turn will inform the driver of the fault via the CCDIC display. If the BCM becomes unable to communicate with an OSM or the LSP, it will log a lighting malfunction code and inform the driver of a "Lighting Fault" via CCDIC display. In some cases the BCM will substitute one lamp for another to maintain near normal operation.