Self-Diagnostic System: Description: Notes
WARNING: This page is about a different car, the 1990 Oldsmobile Cutlass Cruiser, 1990 Oldsmobile Cutlass Ciera, 1990 Oldsmobile Cutlass Calais, 1990 Buick Skylark, and 1990 Buick Century. 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.