Tips December 2, 2025 5 min read

5 Things to Know Before Your First Smog Check

First-time smog check? Don't stress. Here's what every California driver should know before their emissions test.

Getting your first smog check can feel a bit mysterious. What happens during the test? What if you fail? How do you even prepare?

Relax—it's simpler than you think. Here are 5 things that'll help you pass on your first try and avoid any surprise failures.

01

Drive Your Car for 20+ Minutes Before the Test

This is the #1 tip technicians wish everyone knew. Your engine and catalytic converter need to be at full operating temperature for accurate readings.

Why it matters: Cold engines produce different emissions. If you drive to your appointment and arrive with a cold engine, you might fail tests you'd normally pass.
02

Your Check Engine Light Must Be Off

This is non-negotiable. If your check engine light is on, you'll automatically fail the smog check—even if the underlying issue doesn't affect emissions.

What to do: If your light is on, get it diagnosed at an auto shop first. Fix the issue, let the light turn off naturally, then schedule your smog check.
03

Don't Clear Error Codes Right Before the Test

Here's a common mistake: people clear their check engine codes thinking it'll help them pass. It won't—it'll actually cause you to fail.

Technical reason: When codes are cleared, your car's "readiness monitors" reset. The smog test checks these monitors, and if they're not ready, you'll fail. After clearing codes, drive 100-200 miles before testing.
04

Basic Maintenance Helps You Pass

Your car's emissions system works best when everything else is maintained. A few simple things make a difference:

Quick checklist:
  • Check that your gas cap seals properly
  • Make sure your air filter isn't clogged
  • If you're due for an oil change, do it before the test
  • Ensure your tires are properly inflated
05

Book Online and Know What You're Walking Into

Not all smog stations are created equal. Some are faster, some are cheaper, some offer better service. Do a little research before you go.

Pro tip: On Lokali, you can compare prices, read reviews, and book your appointment online. You'll know exactly what to expect before you arrive—no surprises.

What Happens During a Smog Check?

Now that you're prepared, here's what to expect when you arrive:

  1. Check-in: You'll provide your vehicle info and payment (usually $50-90)
  2. Visual inspection: The technician checks your emission control systems
  3. OBD connection: They plug into your car's computer to read diagnostic codes
  4. Functional test: They verify your check engine light and other systems work
  5. Results: You get a pass certificate or a failure report (usually in 15-20 minutes)

That's it! If you pass, your results are electronically sent to the DMV. If you fail, you'll get a detailed report explaining why and what needs to be fixed.

What If You Fail?

Don't panic. Most failures are fixable. Common causes include:

California also has a Consumer Assistance Program that can help with repair costs if you qualify.

Ready for Your First Smog Check?

Find verified stations near you, compare prices, and book instantly.

Book Your Smog Check →