What Is MIL (Malfunction Indicator Lamp)?

The Check Engine Light or Service Engine Soon light on the dashboard, officially called the Malfunction Indicator Lamp in OBD-II specifications.

The MIL illuminates when the OBD-II system detects an emissions-related fault and stores a DTC. A steady MIL indicates a confirmed fault that needs attention. A flashing MIL indicates a severe misfire condition that could damage the catalytic converter, requiring immediate service. The MIL may turn off automatically if the fault condition is no longer detected after three consecutive drive cycles.