Self-Diagnostic System: Notes

NOTE: Powertrain Control Module (PCM) is also be referred to as Electronic Control Module (ECM) in some diagnostic charts and figures. Terms are used interchangeably.

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

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 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.