Self-Diagnostic System: Notes

NOTE: Diagnostic trouble code tests are written specifically for use with GM Tech I or Tech II scan tools. Generic scan tool can be used but may have limited functions. This article only covers the portion of those systems which relates to body control system diagnosis. For further information, see appropriate Diagnostic System Check for the system in which customer concern is addressed.

Body Control Module (BCM) is equipped with a self-diagnostic system, which detects system Diagnostic Trouble Codes (DTCs) or abnormalities. When a malfunction occurs, BCM will store a DTC. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . Malfunctions are recorded as history/intermittent failures or as current failures. Current DTCs indicate BCM has detected a malfunction which is currently present. A history DTC indicates that BCM has previously detected a malfunction that is not currently present.

The BCM Diagnostic System Check is the starting point for identifying which module(s) on the class 2 serial data circuit is responsible for issuing the DTC. The Diagnostic System Check will direct the technician to the correct diagnostic procedure for the identified module.