Self-Diagnostic System: Description: Notes
WARNING: This page does not describe the selected car, but rather 11 other vehicles, including the 1990 Pontiac Grand Prix, 1990 Pontiac Firebird, 1990 Pontiac 6000, 1990 Oldsmobile Cutlass Supreme, and 1990 Chevrolet Lumina. However, it is still accessible from the selected car via links, so may be relevant.
The ECM is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, ECM will illuminate the SERVICE ENGINE SOON light located on instrument panel. When malfunction is detected and light is turned on, a corresponding trouble code will be stored in ECM memory. To retrieve stored codes, see RETRIEVING CODES (NON-SCAN) in this article. Malfunctions are recorded as HARD FAILURES or as INTERMITTENT FAILURES.