Self-Diagnostic System: Notes

NOTE: For additional information and operating procedures for self-diagnostic system, refer to TESTS W/CODES article. NOTE: Malfunction Indicator Light (MIL) is also known as CHECK ENGINE light.

Self-diagnostic system is capable of detecting ECM malfunctions and storing related trouble code. Since intermittent codes are also stored, all codes are available for interpretation, unless codes have been cleared since malfunction last occurred.

Self-diagnostic system will be operated in one of 2 Modes. Modes are manually changed using screwdriver through access port on side of ECM to rotate diagnostic test mode selector. Mode I is normal vehicle operating mode and provides a MIL bulb check (ignition on and engine off) and malfunction warning (ignition on and engine running). Mode II is for displaying diagnostic trouble codes and monitoring HO2S (air/fuel mixture feedback control). MIL located on dash will flash simultaneously with Red LED located on ECM.