Self-Diagnostic System: Overview: Notes

WARNING: This page does not describe the selected car, but rather 19 other vehicles, including the 1996 Chevrolet Chevy Van, 1995 GMC Yukon, 1995 GMC Vandura Special, 1995 GMC Vandura, and 1995 GMC Suburban. However, it is still accessible from the selected car via links, so may be relevant.

All vehicle are equipped with either an Electronic Control Module (ECM), Powertrain Control Module (PCM) or Vehicle Control Module (VCM). Unless specifically stated, references to ECM also apply to PCM or VCM equipped vehicles.

The control module is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, control module will illuminate the SERVICE ENGINE SOON light located on instrument panel. This light is also referred to as the Malfunction Indicator Light (MIL). When malfunction is detected and MIL is turned on, a corresponding trouble code will be stored in control module memory. To retrieve stored codes, see READING TROUBLE CODES or RETRIEVING CODES (NON-SCAN) . Malfunctions are recorded as HARD FAILURES or as INTERMITTENT FAILURES.

NOTE: Not all trouble codes will turn on the SERVICE ENGINE SOON light. All emission-related codes will turn on the SERVICE ENGINE SOON light.