How Arizona's emissions testing works

Arizona requires emissions testing for most vehicles registered in Maricopa and Pima counties — the state's two most populated areas. If you live outside those counties, you do not need to test. The test itself measures what comes out of your tailpipe: carbon monoxide, nitrogen oxides, and particulate matter. A machine reads your vehicle's onboard diagnostic system and compares the results to state standards.

You can test at any Arizona Department of Environmental Quality (ADEQ) certified emissions testing station. These are private repair shops and testing facilities scattered throughout the state, not government offices. The test takes about 10 to 15 minutes and costs between $20 and $30, depending on the station. You do not need an appointment at most locations, though some accept them.

Your vehicle must pass before you can renew your vehicle registration. If it fails, you have 30 days to fix the problem and retest at no additional charge at the same station. If you pass, the station sends your results electronically to ADEQ, and you can renew your registration when ready.

Key Takeaways

  • Emissions testing is required only in Maricopa and Pima counties; if you live elsewhere in Arizona, you do not need to test.
  • You can test at any ADEQ-certified private station, which you can find on the ADEQ website by entering your zip code.
  • The test costs $20 to $30 and takes 10 to 15 minutes; results go directly to the state, so you can renew registration right away if you pass.
  • If your vehicle fails, you have 30 days to repair it and retest for free at the same station before your registration expires.
  • Vehicles older than 1975 and some diesel trucks are exempt from testing, but most cars and light trucks registered in the two counties must test every two years.

Which vehicles must be tested in Arizona

If you register your vehicle in Maricopa or Pima county, you almost certainly need to test — unless your vehicle falls into a specific exemption. Vehicles manufactured before 1975 do not test. Diesel-powered vehicles weighing more than 14,000 pounds do not test. Some alternative-fuel vehicles, like those running on natural gas, may be exempt depending on the model year and fuel type.

Electric vehicles do not test. Vehicles with a salvage title do not test. If you are unsure whether your vehicle is exempt, the ADEQ website has a lookup tool where you enter your vehicle identification number (VIN) and registration county, and it tells you whether testing is required.

When you need to test and how often

Testing is required every two years in both Maricopa and Pima counties. Your registration renewal notice will tell you the important date. You can test up to 90 days before your registration expires, so you have a window to schedule it without rushing.

If you recently moved to Arizona from another state, you must test before you can register your vehicle here, even if it was just tested in your previous state. Arizona does not accept out-of-state test results.

Finding a testing station and what to bring

The ADEQ website has a searchable list of certified testing stations organized by county and city. You can search by zip code or station name. Most stations are open during regular business hours, Monday through Friday, and some open on Saturday mornings. Call ahead if you want to confirm hours or ask whether they accept walk-ins.

Bring your vehicle registration and a valid photo ID. The station will need your VIN, which is on your registration and on the dashboard at the base of the windshield on the driver's side. If you have had recent work done on your vehicle — especially emissions-related repairs — bring the receipt. Some stations ask for it, and it can help explain a borderline result.

What happens if your vehicle fails the test

A failure means your vehicle's emissions are above Arizona's limits. The station will give you a printed report showing which pollutants exceeded the standard. Common reasons for failure include a faulty oxygen sensor, a loose gas cap, a clogged air filter, or an engine problem that triggers the check-engine light.

You have 30 days from the test date to repair your vehicle and retest at the same station for free. You do not pay again. If you retest within 30 days and pass, your registration can be renewed. If you do not retest within 30 days, your registration will expire and you cannot legally drive the vehicle.

If repairs are expensive and your vehicle is old, you may want to get a second opinion from a mechanic before spending money. Some repairs are straightforward and cheap — a new gas cap costs $5 to $10 — while others, like replacing a catalytic converter, can cost hundreds of dollars.

Passing your test and renewing registration

Once your vehicle passes, the testing station sends the result to ADEQ electronically. You do not have to do anything else. You can then renew your vehicle registration through the Arizona Department of Transportation (ADOT) website, by mail, or in person at an ADOT office. You will need your registration renewal notice and proof of insurance.

You do not need to bring the emissions test result to ADOT — the two agencies share the information automatically. If you renew online or by mail, the process takes a few days. If you go in person, you can renew when ready.

Vehicles that are exempt from testing

Beyond the year and fuel-type exemptions mentioned earlier, a few other categories do not test. Motorcycles do not test. Vehicles with a gross vehicle weight rating over 14,000 pounds do not test. Vehicles registered as collector cars or historic vehicles do not test. If your vehicle has a salvage, rebuilt, or non-repairable title, it does not test.

If you are unsure, the ADEQ lookup tool is the fastest way to confirm. Enter your VIN and county, and it will tell you whether your vehicle is exempt or required to test.

Frequently Asked Questions

Can I test in a different county than where I live?

Yes. You can test at any ADEQ-certified station in Arizona, regardless of which county you live in. However, your vehicle must be registered in Maricopa or Pima county for testing to be required at all. If you are registered in a different county, you do not need to test.

What if I fail the test twice?

If you fail a retest within the 30-day window, you can test again. There is no limit to how many times you can retest within 30 days, and each retest at the same station is free. After 30 days, you must pay the full fee again if you want to test.

Do I need to test if I just bought a used car in Arizona?

If the car is registered in Maricopa or Pima county, yes — you must test before you can renew the registration. If the previous owner just renewed it, you may have time before the next renewal is due. Check your registration notice for the expiration date.

What if my check-engine light is on?

You can still test with the check-engine light on. However, the light usually means your vehicle will fail the emissions test. Have a mechanic diagnose the problem first — it could be something straightforward like a loose gas cap, or it could be a sensor or emissions system issue that needs repair.

Can I get a waiver if my vehicle fails?

Arizona does not issue waivers for failed emissions tests. You must repair your vehicle and retest. However, if you have made a good-faith repair attempt and your vehicle still fails, you may be able to register it under a conditional registration while you continue repairs — contact your local ADOT office to ask about this option.