Fault Detection

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.

While the BCM is scanning each OSM and the LSP, it is making both commands and requests. The data received informs the BCM as to the integrity of the 4 outputs of the OSM. Therefore, if an OSM detects an open or short in one of its outputs, the BCM will be informed of the malfunction and its location immediately. See Fig 1.

The BCM will immediately inform the driver of the problem with the CCDIC display. If the BCM is unable to communicate with either the LSP or the OSM, it will log a lighting malfunction code and inform the driver with a "LIGHTING FAULT" display on the CCDIC.

In some cases the BCM will substitute one lamp for another in order to maintain near normal operation. For a list of lamps the BCM will substitute, refer to LAMP SUBSTITUTION table under DESCRIPTION & OPERATION. Lamp substituted will be on the same side of the car as is the lamp that is malfunctioning.

Fig 1: Locating Output Switching Modules

Courtesy of GENERAL MOTORS CORP.