California Smog Check: What Pasadena Drivers Need to Know

If you drive in California, the smog check is part of life. It's also one of the most confusing parts of owning a car: when is it due, who pays when you sell, what does "STAR station" mean, and why did a car that runs fine fail? Here's a plain-English guide from the team at Walnut Smog & Repair, a STAR Certified station in Pasadena.

When you need a smog check

• Biennial (every two years): Most gasoline vehicles 1976 and newer need a smog check every other registration renewal once they're more than eight model years old. Newer vehicles pay a smog abatement fee instead. Your DMV renewal notice tells you whether a smog check is required this year.
• Change of ownership: When a vehicle more than four model years old is sold, the seller is generally responsible for providing a valid smog certificate. The certificate is good for 90 days.
• New to California: Most vehicles coming from out of state need a smog check to be registered here.
• Diesels: 1998 and newer diesel vehicles with a gross vehicle weight rating up to 14,000 lbs are part of the program.

Who's exempt

Electric vehicles, motorcycles, gasoline vehicles 1975 and older, and some natural gas and heavy vehicles are exempt. Rules change from time to time, so check your DMV notice or the Bureau of Automotive Repair (BAR) website for your specific vehicle.

What the test includes

Visual inspection

The inspector checks that the required emissions equipment is present, connected and not modified. Aftermarket parts need to be approved for use in California. A missing or non-approved catalytic converter fails here.

Functional checks

This includes checking that the check engine light works and isn't on, and other system checks depending on the vehicle.

Emissions test

Newer vehicles get an OBD test, where the equipment reads what the car's computer reports through the diagnostic port. Older vehicles, generally 1999 and earlier, get a tailpipe test that measures what actually comes out of the exhaust, often on a dynamometer that lets the car run at speed while it's stationary. That's the dyno you'll see in our bay.

What does "STAR station required" mean?

Some renewal notices say the vehicle must be tested at a STAR station. STAR stations meet higher performance standards set by BAR. Walnut Smog & Repair is STAR Certified, so we can test those vehicles. Read more in our STAR station guide.

How to pass the first time

• No check engine light. It's an automatic fail. Get it diagnosed first, see check engine diagnostics.
• Don't clear codes or disconnect the battery right before the test. That resets the readiness monitors and the car can be rejected as "not ready."
• Drive it first. Arrive with the engine warmed up from a real drive, not a cold start around the corner.
• Keep up with maintenance. Fresh oil, a good air filter and healthy spark plugs help older cars on tailpipe tests. See engine tune-up.
• Fix leaks and smoke. Visible smoke or oil leaking onto exhaust parts is a problem on its own.

If your car fails

Don't panic, and don't start replacing expensive parts on a guess. Many failures come down to an oxygen sensor, a vacuum leak or a misfire, not a catalytic converter. One of our customers was sure his '99 Nissan Frontier needed a converter; it needed an O2 sensor. Read what to do after a failed smog check, or see our failed smog repair service.

Get your smog check in Pasadena

Walnut Smog & Repair is at 1323 E Walnut St #2, just off the 210. We're open Monday through Friday, 7:30 AM to 5 PM. Call (626) 449-6252, or learn more about our smog check service.

Book a visit at Walnut Smog