Self-Diagnosis Function (Check Engine Light)

When a sensor signal abnormality occurs, the ECM lights the Malfunction Indicator Light (MIL) and stores the failure code in erasable memory. When the ignition is initially turned on, the ECM supplies ground to the MIL for two seconds to check the bulb.

To prevent false indications, the Two Trip Detection Method is used for the HO₂ S, fuel metering-related systems, idle control system, ECT sensor, EGR system self-diagnostic functions and EVAP control system. When an abnormality occurs, the ECM stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF and ON again, the ECM informs the driver by lighting the MIL.

If misfiring that increases emissions or EVAP control system malfunction is detected during two consecutive driving cycles, or TWC deterioration is detected during three consecutive driving cycles, the ECM turns the MIL on. A "Driving Cycle" consists of starting the engine, beginning closed loop operation, and stopping the engine. To ease troubleshooting, these functions are cancelled when you short the service check connector. The MIL will then blink immediately when an abnormality occurs.