Description of On-Board Diagnostics

ECM Fail-safe/Back-up Functions

1. Fail-safe Function
When an abnormality occurs in a signal from a sensor, the PCM ignores that signal and assumes a pre-programmed value for that sensor that allows the engine to continue to run.

2. Back-up Function
When an abnormality occurs in the PCM itself, the fuel injectors are controlled by a back-up circuit independent of the system in order to permit minimal driving.

3. Self-diagnosis Function [Malfunction Indicator Lamp (MIL)]
When an abnormality occurs in a signal from a sensor, the PCM supplies ground for the MIL and stores the DTC in erasable memory. When the ignition is initially turned on, the PCM supplies ground for the MIL for 2 seconds to check the MIL bulb condition.

4. Two Driving Cycle Detection Method
To prevent false indications, the "two driving cycle detection method" is used for the HO2S, fuel metering-related, idle control system, ECT sensor, EGR system, TWC and EVAP control system and other self-diagnostic functions. When an abnormality occurs, the PCM stores it in its memory. When the same abnormality recurs after switch is turned OFF and ON (II) again, the PCM informs the driver by turning on the MIL.