Self-Diagnostic System: Notes

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. Malfunctions are designated as either "hard failures" or "intermittent failures". To retrieve stored codes, see appropriate TESTS W/CODES article in this section.

In addition to hard failures and intermittent failures, Saturn models also store information flags and codes in malfunction history. Information flags indicate a failure and will not turn on the SERVICE ENGINE SOON light. Information flags and codes stored in malfunction history are used as a diagnostic tool to help technician when hard codes or intermittent problems occur.