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:

• The fuel control heated oxygen sensors (HO2S)
• The catalyst monitoring heated oxygen sensors
• The engine coolant temperature (ECT) sensor
• The throttle position (TP) sensor
• The mass air flow (MAF) sensor
• The vehicle speed sensor (VSS)
• The intake air temperature (IAT) sensor
• The manifold absolute pressure (MAP) sensor
• The camshaft position (CMP) sensor
• The crankshaft position (CKP) sensor
• The evaporative emission (EVAP) control system
• The idle air control (IAC) system
• The misfire detection
• The fuel trim
• The catalyst monitor
• The cooling fan control
• The 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.