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.

Why is the CHECK ENGINE LIGHT ON?

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