Why Did My Car Fail Smog? (And What to Do Next)

Most smog failures come down to six causes, and most are fixable. Your vehicle inspection report lists the exact reason. Match it to the list below.

Check engine light is on: the car's computer has stored an emissions fault. It's an automatic fail until the problem is repaired.

"Not ready" monitors: after a battery change, a dead battery, or cleared codes, the car's self-tests reset. Drive normally for a week or two (a mix of city and freeway) and come back.

Modified engine software: a tune that isn't factory or California-approved fails, even if the car runs fine.

Missing or non-approved parts: the visual inspection fails cars with a missing catalytic converter (often from theft) or aftermarket parts without a CARB approval number.

A part that doesn't work as designed: the functional check catches problems like a faulty EGR or evaporative system.

High tailpipe readings: pre-2000 cars get a tailpipe test, and worn engines or bad sensors can push the numbers over the limit.

Help paying for repairs: California's Consumer Assistance Program (CAP) helps eligible drivers pay for emissions repairs, or pays you to retire a car that isn't worth fixing. Check if you qualify at bar.ca.gov/cap.

What to Do Next

• Read your report and ask us to walk you through it. It's free to ask.

• Check your warranty. Some emissions parts are covered longer than the regular warranty; your owner's manual lists them.

• Get the repair done at a licensed test-and-repair or repair-only station.

• Come back for a retest. If your DMV notice says STAR, the retest must be at a STAR station.

• Unusual case (engine swap, kit car, hard-to-find parts, or a disputed result)? The state's Smog Check Referee can help at asktheref.org.

• Don't wait on it: your registration can't be renewed without a passing smog. Call (209) 800-1312 and we'll help you find the fastest way to a pass.