Background

Background

The Malfunction Indicator Lamp shows when there is a problem with the engine or emissions components.

The PCM is responsible for continuously adjusting air and fuel mixtures in the engine to maximize performance and efficiency. When the OBD-II system detects a problem, it ‘throws’ a Diagnostic Trouble Code, or DTC. Diagnostic trouble codes can be interoperated by a computer, and the specific source of the code can often be identified. When an emissions problem occurs, the MIL (Malfunction Indicator Lamp) illuminates. If the problem is severe, MIL will flash to indicate conditions that could damage the catalyst. 

This is the MIL Status Screen. During the emissions test, it’s the inspectors duty to accurately mark whether the MIL light is illuminated.