Fault Detection

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. The LAMP SUBSTITUTION  table shows the substitutions the BCM will make. If a system fault is detected that would disable the communication among all OSM's and the BCM, the BCM will activate the redundant relays which will power the left low beam lamp and the left outer upper tail lamp. This action eliminates the possibility of total loss of lighting.