Guides

Emissions Testing & Smog Check Guides

Learn everything you need to know about emissions tests and smog checks. These step-by-step guides cover preparation, costs, state requirements, what happens during the test, common failure reasons, and how to pass your inspection on the first try.

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About Our Emissions Testing Guides

Our guides are written to help drivers understand emissions testing requirements, prepare for inspections, and know what to do if something goes wrong.

What You'll Learn

Each guide focuses on a specific topic related to emissions testing and smog checks. Whether you're preparing for your first test, dealing with a failure, or trying to understand exemptions, our guides break down complex regulations into clear, actionable information.

  • How to prepare your vehicle for an emissions test
  • What happens during OBD-II and tailpipe inspections
  • Common reasons vehicles fail and how to fix them
  • Exemptions for classic cars, diesels, EVs, and hybrids
  • State-specific rules and where testing is required
  • What to do if your vehicle fails inspection

Updated for 2025

Emissions programs change as states update their Clean Air Act compliance plans. All guides are reviewed and updated to reflect current 2025 requirements, procedures, and regulations.

Find Your State's Requirements

Frequently Asked Questions About Our Emissions Testing Guides

Find answers to common questions about our emissions testing and smog check guides, what they cover, and how to use them.

Each guide focuses on practical, general advice that applies in most emissions testing programs. Many articles also include state-specific examples or links to state pages. For exact rules in your area, like which model years must test or which counties require smog checks, use the Browse States section and read your state's dedicated page.
Yes. The same basics apply: OBD-II checks, readiness monitors, and avoiding check-engine-light failures. California's Smog Check program has extra rules and terms (like STAR stations) that differ from other states. Where needed, our guides call out California-specific requirements and link to additional resources.
Yes. Many guides include sections for gasoline, diesel, hybrid, and electric vehicles. Topics like opacity testing or heavy-duty diesel inspections are specific to diesel vehicles and are clearly labeled so you can find what applies to your vehicle type.
Several guides are written specifically for failed emissions tests. They cover what the failure report means, how retests work, how to handle repair cost limits, and when waivers or hardship programs might be available. They're a good starting point before talking to a mechanic.
We review and update guides regularly to reflect current 2025 testing rules, model-year cutoffs, and program changes. When a state ends or changes its emissions testing program, we update affected guides and state pages so you're not relying on outdated information.
Start with our Moving to a New State: Emissions Test Requirements Checklist guide. It explains how new-resident rules work, when you need to test, and whether a recent smog check from another state still counts. Then visit your new state's page for detailed local requirements.
Yes. If you don't see a guide that answers your question, contact us with topic suggestions. We regularly add new guides based on common driver questions and changes in state programs.

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