The short answer, no. Regardless of whether your check engine light has to do with emission issues or not, you will be automatically failed for having your check engine light triggered. Some Sparks and Reno repair shops won’t even smog your car at all if you have a check engine light on!
This means you must never have a check engine light on when you go to do a smog test. However, this does not mean you can unplug and plug in your car battery to reset the check engine light and other various engine codes. Even if the check engine light is off if the problem still persists during the smog test the code will come back up and you will fail.
If you recently have had issues with your check engine light before smogging it and took it to a diesel repair shop, it may be the repair shop didn’t reset your engine code. After work is done on a problem which triggered your check engine light to come on, the engine codes will remain on until they are reset. This can be reset by removing the connectors on the battery’s terminals and placing them back on or using an OBD2 Scanner to erase the engine code.
As unfair as it may seem to get failed for your vehicle’s malfunctions, the reason they will fail you immediately is because when the light is on, your engine’s emission control system may stop reading information in real time. This causes poor emissions and could end up resulting in a car that releases smoke and does not properly drive. The best way to get around a check engine light is to visit a Reno/Sparks Diesel repair shop like Wayne’s Automotive Center and have your mechanic handle the repairs so you can pass smog without any worries!