What Aurora requires for emissions testing

Aurora, Colorado requires emissions testing for most vehicles registered in the city, though the exact rules depend on your vehicle's age, type, and fuel source. Gasoline vehicles typically need testing every two years; diesel vehicles and those over 25 years old have different schedules or may be exempt. You'll take your car to an Authorized Emissions Test Facility — these are private shops certified by the Colorado Department of Public Health and Environment, not a single government testing center.

The test itself takes about 30 minutes and costs between $25 and $35, though prices vary by facility. The technician will plug a diagnostic scanner into your vehicle's onboard computer port (located under the dashboard on the driver's side) to read emissions data. For older vehicles without this port, a tailpipe test measures what actually comes out of your exhaust. Your vehicle must pass within the emissions limits set by Colorado law, which are stricter than federal standards.

You can't renew your vehicle registration in Aurora without a passing test result on file. The test result is sent electronically to the Colorado Division of Motor Vehicles, so you don't need to carry a paper certificate — though the testing facility will give you one anyway.

Key Takeaways

  • Aurora requires emissions testing every two years for most gasoline vehicles, with different rules for diesel, hybrid, and vehicles over 25 years old.
  • You must visit a private Authorized Emissions Test Facility; the test costs $25 to $35 and takes about 30 minutes.
  • The technician reads your vehicle's onboard computer data or performs a tailpipe test, depending on your vehicle's age and type.
  • A passing result is sent automatically to the Colorado Division of Motor Vehicles and is required before you can renew your registration.
  • A failing test means you need repairs and a retest, which costs another testing fee; some facilities offer free retests within 30 days if you use them for repairs.

Which vehicles need testing in Aurora

Not every vehicle registered in Aurora must be tested. Gasoline-powered cars, SUVs, and light trucks registered in Aurora need testing every two years if they were built in 1975 or later. Diesel vehicles have their own schedule: they need testing every two years if built in 1997 or later. Hybrid vehicles follow the same two-year schedule as gasoline vehicles.

Vehicles built before 1975, motorcycles, and vehicles with permanent disabled-person license plates are exempt. Electric vehicles are also exempt — they produce no tailpipe emissions. If you're unsure whether your vehicle is required, the Colorado Division of Motor Vehicles website has a lookup tool, or you can call an Authorized Emissions Test Facility and give them your vehicle's year, make, and model.

Your registration renewal notice will tell you whether testing is required. If it says "emissions test required," you must have a passing result before the renewal important date or your registration will not be renewed.

What causes a vehicle to fail the Aurora emissions test

A vehicle fails when its emissions exceed Colorado's limits for nitrogen oxides (NOx), particulate matter, or other pollutants. The most common reason is a check engine light that's already on — if the light is illuminated, the vehicle will fail automatically, even if the actual emissions numbers are borderline. A malfunctioning oxygen sensor, a faulty catalytic converter, or a leak in the fuel system are frequent culprits.

Older vehicles with high mileage fail more often because engine wear increases emissions. A vehicle that's been well-maintained — with regular oil changes, a clean air filter, and a functioning catalytic converter — is far more likely to pass. Driving with low tire pressure or using the wrong octane fuel can also push emissions higher, though these are usually straightforward fixes.

If your vehicle fails, you'll receive a detailed report showing which emissions standard it exceeded. You then have 30 days to get repairs done and return for a retest. Some facilities offer a free retest within that window if you have them perform the repairs, which can save you the $25 to $35 retest fee.

How to find an Authorized Emissions Test Facility in Aurora

The Colorado Department of Public Health and Environment maintains a searchable list of all Authorized Emissions Test Facilities on its website. You can filter by location and see which facilities are in or near Aurora. Each facility's listing shows its address, phone number, and hours of operation.

Call ahead before you go. Ask whether they have same-day or next-day appointments, what they charge, and whether they offer a free retest if you use them for repairs. Some facilities are busier than others, especially near the end of the month when people rush to renew registrations. A few facilities in the Aurora area also offer basic repairs — if your vehicle fails, they can often diagnose and fix the problem on the spot, then retest you the same day.

Bring your vehicle registration and proof of insurance. The technician will need your vehicle identification number (VIN), which is on your registration and also visible on the dashboard at the base of the windshield on the driver's side.

What happens if your vehicle fails the test

A failing result does not prevent you from driving your vehicle — it only prevents you from renewing your registration. You have 30 days from the test date to get repairs and pass a retest. During that time, you can still drive on your current registration as long as it hasn't expired.

Take the failure report to a repair shop. The report will list the specific emissions standard your vehicle exceeded, which helps the mechanic know where to look. Common repairs include replacing the oxygen sensor ($150 to $300), fixing a vacuum leak ($100 to $400), or replacing the catalytic converter ($800 to $2,500, depending on your vehicle). Some repairs are straightforward and inexpensive; others are costly.

After repairs, return to the testing facility for a retest. If you pass, the new result is sent to the Division of Motor Vehicles and you can renew your registration. If you fail again, you have another 30 days to try again. Some people take their vehicle to a different repair shop for a second opinion if the first repair didn't work.

Repair information and hardship waivers

Colorado offers a Repair information Program that can help pay for emissions-related repairs if your household income is at or below 200% of the federal poverty line. The program covers up to $500 per vehicle per year. You must explore through your county's air quality office; in Aurora, that's the Tri-County Health Department. The process requires proof of income and a repair estimate from a shop.

If you cannot afford repairs even with information, Colorado also has a Hardship Waiver that allows you to renew your registration without a passing test if you've made a good-faith effort to repair the vehicle. This requires documentation: proof that you've obtained repair estimates, proof of income, and evidence that you cannot afford the repairs. The waiver is not automatic — you must request it from your county air quality office and meet specific criteria.

Contact the Tri-County Health Department in Aurora for information about both programs. The process process takes a few weeks, so explore early if you think you'll need help.

Preparing your vehicle before the test

Before you schedule a test, make sure your vehicle is in reasonable condition. Check that the check engine light is off — if it's on, get the vehicle scanned for codes before testing. Top off your fuel tank; a nearly empty tank can sometimes trigger a false reading. Make sure your tires are inflated to the pressure listed on the driver's door jamb, not the maximum pressure on the tire itself.

Drive your vehicle for at least 20 minutes before the test, including some highway driving if possible. A "warmed-up" engine runs cleaner and is more likely to pass. Avoid driving through puddles or wet grass when ready before the test, as moisture can affect the readings.

If your vehicle has been sitting unused for weeks, it may fail even if it's mechanically sound. Run it regularly for a few days before testing. If you know your vehicle has had emissions problems in the past, consider a pre-test diagnostic scan at a repair shop ($50 to $100) to catch problems before you pay for the official test.

Frequently Asked Questions

Can I test my vehicle outside Aurora to avoid testing?

No. Your vehicle is subject to Aurora's emissions requirements based on where it's registered, not where you test it. If your registration address is in Aurora, you must pass an Aurora-compliant test. Testing in another Colorado county won't satisfy Aurora's requirement.

What if I just bought a used car in Aurora — do I need to test it before registering it?

Yes, if the vehicle requires testing. You'll need a passing emissions result before you can register it in Colorado. The seller may have a recent passing test on file, which you can use if it's within the testing cycle. Otherwise, you must get a new test before registration.

Do I need to test my vehicle if I'm only renewing my registration online?

Yes. Online renewal still requires a passing emissions result on file. The system will not allow you to complete the renewal without it. You must visit a testing facility first.

How long does a passing test result stay valid?

A passing result is valid for two years from the test date. Your registration renewal notice will tell you when your next test is due. If you renew your registration before the two years are up, you don't need a new test until the next cycle.

What if the testing facility's equipment seems broken or gives me a result I don't believe?

You can request a retest at a different Authorized Emissions Test Facility. Each facility's equipment is calibrated and certified, but if you suspect an error, a second test at another location will give you a definitive answer. You'll pay the testing fee again, but if the second result is significantly different, you can contact the Colorado Department of Public Health and Environment to report the discrepancy.