Diagnostic Procedure Terms: Notes

The dash-mounted "Engine Control System Fault"  telltale is used to inform the technician of detected system malfunctions or abnormalities. These malfunctions may be related to the various ECM inputs or controlled functions or to the ECM itself. The "Engine Control System Fault" telltale that is illuminated by a fault occurrence will automatically go out if the fault clears in most cases.

Some codes will cause the "Engine Control System Fault" telltale light to be illuminated for the entire ignition cycle. If a fault goes away, it is logged as an history trouble code by the ECM. The ECM stores the trouble code associated with the detected failure until the diagnostic codes are "Cleared" or until 50 ignition switch (on-off) cycles have occurred without any fault reappearing.