What should be done if the Malfunction Indicator Lamp (MIL) is illuminated during a Smog Check?

When the Malfunction Indicator Lamp (MIL) is illuminated, it signifies that the vehicle's onboard diagnostic system has detected a problem that could affect emissions. Thus, to ensure compliance with emissions standards and the accuracy of the smog test results, it is critical for the technician to investigate the underlying cause of the MIL's illumination before proceeding with the inspection.

Diagnosing the issue allows the technician to identify any faults in the vehicle’s emission control system, which may include issues with sensors, emissions components, or other related systems. This step is essential because even if the vehicle appears to run adequately, an illuminated MIL indicates potential emissions non-compliance, which may lead to increased pollutants being emitted. Therefore, addressing the issue associated with the MIL is a fundamental aspect of conducting a thorough and responsible Smog Check.