What Arizona's emissions test measures and who has to take it

Arizona requires an emissions test for most vehicles registered in Maricopa, Pima, and Pinal counties — the state's three most populated areas. The test measures what comes out of your tailpipe: nitrogen oxides, particulate matter, and hydrocarbons. A vehicle passes if these pollutants stay below the state's limits for your vehicle's model year and engine type.

You need an emissions test every two years when you renew your vehicle registration, unless your vehicle is exempt. Vehicles registered outside those three counties do not need the test. Vehicles newer than four model years old, motorcycles, diesel trucks over 14,000 pounds, and vehicles with a salvage title are all exempt.

If you buy a used vehicle in Arizona, you do not need a test to complete the purchase — but you will need one when you register it with the Arizona Department of Transportation (ADOT). The seller does not have to provide a passing test result.

Key Takeaways

  • Emissions testing is required every two years in Maricopa, Pima, and Pinal counties when you renew your registration, but not in other Arizona counties.
  • You can take the test at any ADOT-certified emissions testing station, and the test takes about 10 minutes and costs between $20 and $30.
  • If your vehicle fails, you have 60 days to repair it and retest at no additional charge at the same station.
  • Vehicles newer than four model years old and motorcycles are exempt from testing.
  • You must pass the test before ADOT will issue your registration renewal, so plan ahead during busy renewal periods.

Finding a testing station and scheduling your test

ADOT maintains a searchable list of certified emissions testing stations on its website. You can search by county or city to find stations near you. Most stations are independent repair shops, tire shops, or dedicated testing facilities — not all dealerships offer testing.

Many stations accept walk-ins, but calling ahead to confirm hours and current wait times is worth your time, especially during renewal season (typically August through October). Some stations book appointments online or by phone. The test itself takes about 10 minutes once you are in the bay.

Bring your vehicle registration and a valid photo ID. The technician will connect a probe to your vehicle's tailpipe and run the test. You will get a printed result on the spot.

What happens if your vehicle fails the test

A failure means your vehicle's emissions are above the legal limit for its model year. You have 60 days from the test date to repair the vehicle and return to the same testing station for a retest at no charge. The station will note your failure in the system so the retest technician knows to look for it.

Common reasons for failure include a faulty oxygen sensor, a loose or missing gas cap, a malfunctioning catalytic converter, or an engine running too rich (burning too much fuel). A mechanic can run a diagnostic to pinpoint the problem. Some repairs are inexpensive; others cost several hundred dollars.

If you do not retest within 60 days, you cannot renew your registration. ADOT will not issue plates or a registration sticker until you pass. If your registration expires before you pass, you are driving without valid registration, which is a traffic violation.

Cost and timing for emissions testing

The test itself costs between $20 and $30 at most stations. Some stations charge slightly more or less depending on their location and overhead. This is the only fee for the test — ADOT does not charge a separate emissions testing fee on top of your registration renewal.

Plan to take the test at least two weeks before your registration expires, especially if you are renewing during peak months. If you fail and need repairs, the 60-day window gives you time, but waiting until the last week of your registration creates pressure and limits your repair options if a shop is booked out.

If you are renewing your registration by mail or online, you will need to complete the emissions test first and have the passing result in hand before ADOT will process your renewal.

Renewing your registration after a passing test

Once you pass the test, the testing station uploads your result to ADOT's system electronically. You do not need to print anything or bring paperwork to ADOT. When you renew your registration online, by mail, or in person at an ADOT office, the system will show your passing result and allow the renewal to go through.

If you renew online through ADOT's website, the system checks your emissions status automatically. If you renew by mail, include your vehicle identification number (VIN) so ADOT can look up your test result. If you renew in person at an ADOT office, bring your registration and ID; staff will verify the test result on file.

Your registration renewal and your emissions test are two separate transactions. Passing the test does not automatically renew your registration — you still have to complete the registration renewal process through ADOT.

Vehicles that do not need emissions testing

Vehicles registered outside Maricopa, Pima, and Pinal counties are not subject to emissions testing, even if they are driven into those counties regularly. Vehicles newer than four model years old are exempt. Motorcycles, mopeds, and off-road vehicles are exempt. Diesel trucks over 14,000 pounds are exempt. Vehicles with a salvage title or a non-operational status are exempt.

If you own a vehicle that is exempt, you do not need to do anything — just renew your registration normally. ADOT will not ask for an emissions test result.

What to do if you have questions about your specific vehicle

If you are unsure whether your vehicle needs testing, check your registration renewal notice — it will state whether an emissions test is required. You can also call ADOT's customer service line or visit an ADOT office with your VIN and registration. Staff can tell you whether your vehicle is subject to testing based on its age, type, and where it is registered.

If a testing station tells you your vehicle cannot be tested (for example, if the check engine light is on or the vehicle will not start), ask whether the station can perform a visual inspection or whether you need to repair the vehicle first before testing. Requirements vary slightly by station, so calling ahead can save you a trip.

Frequently Asked Questions

Can I test my vehicle in a different county than where it is registered?

Yes. You can take the test at any ADOT-certified station in Arizona, regardless of where your vehicle is registered. The result is valid for registration renewal in your home county.

What if my check engine light is on?

Many stations will not test a vehicle with the check engine light illuminated because the diagnostic system may interfere with the emissions test. Have the vehicle scanned to identify the problem first. Once the issue is repaired and the light is off, you can retest.

Do I need an emissions test if I am buying a used vehicle from a private seller?

No test is required to buy the vehicle. However, when you register it with ADOT, you will need to pass an emissions test before your registration is issued. Plan to take the test within a few days of purchase so you can complete your registration on time.

How long does a passing emissions test result stay valid?

Your result is valid for your two-year registration period. When you renew your registration in two years, you will need a new emissions test. The old result does not carry over.

What if I move out of Arizona after I pass the test?

Your Arizona emissions test result is only valid for Arizona registration. If you move to another state, you will follow that state's inspection and testing rules. You do not need to do anything with your Arizona test result.