Self-Diagnosis Function

The PCM diagnoses any troubles which may occur in the engine control system when the ignition switch is in the On position with the engine running. The PCM indicates a malfunction by illuminating the Malfunction Indicator Lamp (MIL) when a fault occurs in any of the following systems:
^ Heated Oxygen Sensor 1 (HO2S 1)
^ Heated Oxygen Sensor 2 (HO2S 2)
^ Engine Coolant Temperature (ECT) sensor
^ Throttle Position (TP) Sensor, including the CTP switch
^ Mass Air Flow (MAF) sensor
^ Vehicle Speed Sensor (VSS)
^ Intake Air Temperature (IAT) Sensor
^ Manifold Absolute Pressure (MAP) Sensor
^ Camshaft Position (CMP) Sensor
^ Crankshaft Position (CKP) Sensor
^ Evaporative Emission (EVAP) Control System
^ Idle Air Control (IAC) System
^ Misfire detection
^ Fuel-trim
^ Catalyst monitor
^ Cooling fan control
^ Central Processing Unit (CPU) of the PCM

When the PCM detects a malfunction in one of the above areas, the PCM will illuminate or flash the MIL in order to notify the driver of the occurrence of a fault. The PCM will store a Diagnostic Trouble Code (DTC) when the PCM illuminates the MIL.

The PCM will turn off the MIL after 3 consecutive ignition cycles, in which the diagnostic runs, without the malfunction occurring. The DTC will remain stored in the PCM memory after the MIL is OFF.