Malfunction Indicator Lamp (MIL)

The MIL illuminates when a malfunction exists in the engine control system. However, the MIL will not illuminate after three engine starts if the previously recorded malfunction no longer occurs. When the ignition switch is turned ON (before starting the engine), the lamp stays on continuously, which indicates that the malfunction diagnosis system operates normally. The MIL with the "OBD-II" system illuminates when a malfunction occurs in the following components:

– catalytic converter;
– fuel system;
– mass air flow sensor;
– intake air temperature sensor;
– engine coolant temperature sensor;
– throttle position sensor;
– oxygen sensor;
– oxygen sensor heater;
– fuel injectors;
– misfire;
– crankshaft position sensor;
– camshaft position sensor;
– evaporative emission control system;
– vehicle speed sensor;
– idle air control valve;
– electrical power supply;
– ECM;
– transmission malfunction;
– acceleration sensor;
– MIL request signal.

The MIL without the "OBD-II" system illuminates when a malfunction occurs in the following components:

- heated oxygen sensor;
- manifold absolute pressure sensor;
- throttle position sensor;
- engine coolant temperature sensor;
- idle speed control motor;
- fuel injectors;
- ECM.

Inspection

PROCEDURE

1. After the ignition switch is turned ON, the MIL illuminates for 5 seconds, then goes off.
2. If the MIL does not illuminate, check the lamp circuit, the fuse integrity and the lamp condition.

Self-Diagnosis

The ECM constantly monitors input and output signals and other signals under specified conditions. When a malfunction is detected, the ECM stores a diagnostic trouble code in memory and outputs the code to the diagnostic connector. Diagnostic codes can be read using the MIL or the HI-SCAN scan tool. Diagnostic codes remain in memory until the battery cables are disconnected from the battery terminals, the connector is disconnected from the ECM, or the codes are erased using the HI-SCAN scan tool.

If the connector is disconnected with the ignition switch ON, a DTC will be stored in memory. In this case, disconnect the cable from the negative battery terminal for more than 15 seconds to erase the diagnostic memory.