Smog Check: Check Engine Light is on?

Will my car pass a smog check with a CHECK ENGINE LIGHT on?

No, unfortunately your vehicle will fail a smog check if the check engine light is illuminated. The industry term is Malfunction Indicator Lamp (MIL).

The MIL is usually located somewhere on the dash. A proper functioning MIL illuminates when the vehicle is initially started. The MIL then “goes off” a few seconds later. If the MIL stays “on” the vehicle will fail the On Board Diagnostic (OBD) Functional portion of the smog inspection.


It’s a common misconception that an illuminated MIL indicates the need for an oil change or other routine service. An MIL is triggered when the vehicle’s computer finds a problem somewhere in the system. A “trouble code” is set and the MIL is illuminated to notify the driver. Common trouble codes are: faulty gas cap, oxygen sensor, catalytic efficiency, etc. In some way fault codes that illuminate the MIL are always emission related.

Common terms and symbols for an MIL:

  • Check Engine
  • Service Engine Soon
  • A symbol outline of an Engine

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