The most common reasons a car fails a California smog check are a lit check engine light, readiness monitors that haven't finished resetting, missing or modified emissions parts, and high tailpipe readings on older cars. Most of these can be fixed, and several can be avoided just by timing your test right.
The top reasons cars fail
| Reason | What it means | What to do |
|---|---|---|
| Check engine light on | The car's computer has found an emissions-related fault. On 1996 and newer vehicles this is an automatic fail. | Have the code read and the fault repaired before the test. |
| Monitors “not ready” | The car's self-tests haven't finished, usually because the battery was disconnected or codes were cleared recently. | Drive normally for several days, including some highway miles, then test. |
| Visual inspection fail | An emissions part is missing, disconnected or aftermarket without a CARB Executive Order number. | Reinstall the original part or a CARB-approved replacement. |
| High tailpipe readings | On 1999 and older cars, too much HC, CO or NOx. Often a worn catalytic converter, oxygen sensor, or misfire. | Diagnose and repair at a licensed test-and-repair shop. |
| Fuel evaporative leak | On 1976–1995 cars, a leak in the fuel cap, tank or lines. | Replace the gas cap or the leaking line. |
Before your smog check: a short checklist
- Look at your dash. If the check engine light is on, fix that first. A test with the light on is a test the car can't pass.
- Leave the battery alone. If you replaced it or had codes cleared in the last week, give the car a few days of mixed driving.
- Drive at least 20 minutes before you arrive so the engine and catalytic converter are at full temperature.
- Get the oil changed if it's overdue. Dirty oil can raise hydrocarbon readings on older engines.
- Check the gas cap. It should click and seal. A cracked cap can fail the evaporative test.
- Keep the original parts. Intakes, exhausts and tuners need a CARB Executive Order number to be legal.
What happens after a failed smog check
You leave with a Vehicle Inspection Report that lists what failed. Nothing is sent to the DMV as a pass, so your registration can't be renewed yet. Take the report to a licensed repair shop, get the problem fixed, drive the car normally for a few days, and come back for a retest.
Cars that can't be tested normally, such as engine swaps, kit cars, or vehicles with parts the station can't verify, go to a state Smog Check Referee. You can book one through the Bureau of Automotive Repair.
Help paying for smog repairs in Fresno
Consumer Assistance Program (CAP). Run by the Bureau of Automotive Repair. Income-eligible drivers can get money toward emissions repairs, and any owner whose car failed its biennial smog check can apply to retire it for cash. Check eligibility on bar.ca.gov.
Tune In & Tune Up. The San Joaquin Valley Air District and Valley CAN hold free emissions testing events in Fresno, and cars that fail can receive a voucher toward repairs. See upcoming events at valleycan.org.
Ready for a retest?
Bring the car and your previous inspection report. We'll run it again and send the pass to the DMV.