Tips: How to (Legally) Pass Your Next Vehicle Emissions Text

Need to get your vehicle "smogged" to obtain your vehicle registration sticker? Vehicles seven years old need a Smog Check test every other year in order to re-register the car or truck with the California Department of Motor Vehicles and to help California reach its daily goal of removing an extra 100 tons of smog-forming emissions from the air.

The Automobile Club of Southern California ( recommends the following maintenance tips to ensure your vehicle is operating cleanly to pass the state-mandated Smog Check.

"These tips are intended to ensure that vehicles that should pass the Smog Check test do, and are not intended to 'fool' the test equipment," said Auto Club Approved Auto Repair Program Development Manager David Skaien. "These tips are especially important for teens, college students, retirees, telecommuters and others who are 'short trip' drivers. If after following these tips your vehicle fails, then your vehicle needs a professional assessment of its emissions-related systems."

Skaien, who over the years has also held a California Smog Check license, recommends that motorists prepare for the smog test by following these 10 simple tips:


1. Make sure your tires are in good condition and properly inflated.

2. Make sure the "check engine" light or any other dashboard warning lights are NOT on.

3. Make sure that your vehicle has no fluid leaks and no safety issues. Remember, your vehicle will be strapped down on a dynamometer and required to perform flawlessly under stressful conditions.


4. Don't change the size of the tires from the original specifications. The dynamometer test equipment is calibrated to the "stock" tire size. Over- or under-sized tires will alter the speed calculations performed by the test equipment and may prevent your vehicle from going through the test since the machine won't sense the correct speed for your vehicle's tire size.

5. Make sure your vehicle has a clean air filter and fresh engine oil.

6. Make sure your vehicle's gasoline cap fits your vehicle, isn't damaged and is turned tightly in place. A vehicle without a gas cap is an automatic Smog Check test failure.

7. The week of the Smog Check test, take the vehicle out for an extended drive, preferably on the freeway and especially if you're regularly a "short trip" driver. Drive approximately 30 minutes or longer at varying speeds on freeways, surface streets and up hills.


8. Fill the gas tank of your vehicle with the grade of fuel stated in the owner's manual.

9. Make sure all fluids are topped off and that all non-essential items are removed from the trunk or the rear of the vehicle. The dynamometer weighs your vehicle before the test, and if the vehicle is heavier than it should be, the weight will make it harder to pass.

10. Drive at least 30 minutes before arriving at the Smog Check test facility to ensure the car or truck has reached full operating temperature. Ask the repair facility if they can perform the test within 15 minutes of your arrival. This will let the vehicle return to normal operating temperature quickly. Remember to bring the DMV renewal notice with you to the repair facility. The paperwork has a bar code on it that needs to be scanned for the Smog Check test. If you don't have the paperwork, the repair facility may charge you for the extra time it takes to input the vehicle identification number that they could pick up from the bar code.

American Automobile Association:

Auto inspection and maintenance (I/M) programs require the testing of motor vehicles in parts of the country with unhealthy air and the repair of those that do not meet standards. For drivers who don't live in California, but are more interested in an national overview of the I/M program, an EPA document, A Consumer Guide to Auto Emission Inspection and Maintenance Programs, can be accessed at

This article originally appeared in the 08/01/2005 issue of Environmental Protection.

Featured Webinar