How to Pass A Smog Test

Check engine light should not be on. An illuminated check engine light will cause your vehicle to not pass the emissions test automatically. A certified emissions repair shop can use a trouble code retrieval tool to extract trouble code data from the ECU and perform necessary repairs to turn the check engine light off.

If your vehicle's battery has recently been disconnected due to it having needed replacement or battery charging, or if your vehicle recently needed a jump start, we recommend holding off on getting the smog check for at least one week while you drive your vehicle regularly. Chances are while your vehicle's computer lost power, its internal self-test monitors were erased. Without these important and required emission monitors your vehicle cannot pass the smog test. You will be required to drive between 100-200 miles and over the course of a week in order to reset or "complete" the emission monitors. This period of driving is referred to as a "Drive Cycle".

Higher quality fuel will burn cleaner and improve your chances of passing inspection. This does not mean pumping higher Octan fuel such as 89 or 91 if your car does not require it. We recommend using Fuel with high quality additives which such as Chevron prior to your test. The additives will help with cleaning and better burn in your engine.   

A warmed up engine is going to have a better chance of passing the smog test. Drive for a minimum of 20 minutes before heading to the inspection station. This will give the engine enough time to get warm so that it will have proper combustion.

If you haven't performed an oil change within the last 5,000 miles, go ahead and do it before the emissions test. This will assist in getting passing emission test results. Your vehicle's Positive Crank Ventilation (PCV) system is designed to allow the engine to breath fumes from the oil compartments. The fumes are then burned through the combustion process. If the oil in your engine is contaminated due to inadequate oil changes it may very well cause your vehicle to fail the emissions test. Contaminated oils are high in Hydrocarbons (HC) and will present a rich mixture to the combustion chambers. Not performing regularly required oil and filter changes not only causes premature engine wear but can also cause your vehicle to not pass the emissions inspection.

If your vehicle is model year 1999 or older it will be driven on a dynomometer while a sample of its exhaust is collected by the smog machine. Making sure your vehicle's tire pressures are even and correct will allow the vehicle to be driven with greater stability and accuracy during the smog exam.

This will improve the overall emissions output of your vehicle by allowing the engine to maintain a constant and steady load. Correct and even tire pressure may be the deciding factor between a borderline vehicle failing or passing the smog test. This passing tip, as well as tips number 5 and 7 do not necessarily apply to your vehicle if it's 2000 model year or newer; this is not to say your vehicle's tires shouldn't be properly inflated, of course.