Self-Diagnostic System: Notes

The ECM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, ECM illuminates the SERVICE ENGINE SOON light located on instrument panel. When malfunction is detected and light is turned on, a corresponding trouble code is stored in ECM memory. Malfunctions are designated as either "hard failures" or "intermittent failures". For procedures on retrieving stored codes, see appropriate TESTS W/CODES article in the ENGINE PERFORMANCE Section.