What Colorado requires and who has to test

Colorado requires emissions testing for most vehicles registered in the state, but the rules depend on where you live and what you drive. If you live in the Denver metro area, the North Front Range (around Fort Collins), or the Vail Valley, your vehicle must pass an emissions test every two years. If you live elsewhere in Colorado, you do not need emissions testing — your registration renewal is simpler.

Diesel vehicles, motorcycles, and vehicles model year 1981 and older are exempt from testing statewide. Vehicles registered as classic cars or antiques also do not need to test. If you just bought a used vehicle from out of state and are registering it in Colorado for the first time, you will need a test before you can complete registration, even if you live in a non-testing area.

The Colorado Department of Public Health and Environment (CDPHE) sets the standards, but the actual testing is done by private repair shops and testing stations that hold a state license. You choose where to go — there is no single government testing center.

Key Takeaways

  • Colorado emissions testing is required every two years only in the Denver metro area, North Front Range, and Vail Valley; other parts of the state do not require it.
  • You can take your vehicle to any licensed emissions testing station — usually a repair shop or quick-lube facility — and the test takes about 15 minutes.
  • The test costs between $20 and $40 depending on the station, and you pay at the time of testing regardless of whether you pass or fail.
  • If you fail, you have until your registration expires to retest at no additional charge at the same station, or you can pay to test elsewhere.
  • You cannot renew your vehicle registration online or by mail if a test is required — you must show proof of a passing test first.

Finding a testing station and scheduling

The CDPHE maintains a searchable list of licensed testing stations on its website at cdphe.colorado.gov. You can search by county or city to find stations near you. Most are independent repair shops, chain shops like Firestone or Midas, or quick-lube facilities — any shop with a state emissions testing license can do the work.

You do not need an appointment at most stations. You can drive in during business hours, hand over your keys and registration, and the technician will run the test while you wait or sit in the waiting area. The whole process usually takes 10 to 20 minutes. Some stations do accept appointments, so if you want to may provide a short wait, call ahead.

Bring your vehicle registration or proof of ownership and your keys. The technician will plug a diagnostic scanner into your vehicle's onboard computer port to read emissions data. The test does not involve removing any parts or doing any work to your vehicle — it is purely a data read.

What happens during the test and what the results mean

The emissions test measures whether your vehicle's exhaust meets Colorado's standards for nitrogen oxides, particulate matter, and other pollutants. The technician connects a scanner to your vehicle's diagnostic port (usually under the steering wheel or dashboard) and runs a scan that takes a few minutes. For most vehicles, that is the entire test.

You will receive a printed result sheet when ready. If your vehicle passes, the sheet will show a passing status and a confirmation number. The testing station sends the result electronically to the state, and you can then renew your registration. If your vehicle fails, the sheet will show which emissions standards it did not meet and may suggest common causes — a loose gas cap, a faulty oxygen sensor, or a check engine light that needs attention.

A failing result does not mean your vehicle is unsafe or that you have broken a law. It means your vehicle did not meet the state's emissions threshold at that moment. Many vehicles fail because of a straightforward issue like a loose fuel cap or a sensor that needs replacement. You have until your registration expires to fix the problem and retest.

Retesting after a failure and repair options

If you fail, you can retest at the same station at no charge within a set window (usually 30 days, but confirm with your station). You can also pay to test at a different station if you prefer. The retest fee is the same as the initial test — between $20 and $40.

You are not required to have the station repair your vehicle. You can take the failure notice to any mechanic, get a diagnosis, make repairs yourself, or do nothing and straightforward retest elsewhere. Some stations offer repair services and may suggest fixes, but you have no obligation to use them. If you do choose to have repairs done at the testing station, those costs are separate from the test fee and depend on what needs fixing.

Common repairs that help vehicles pass include replacing a faulty oxygen sensor, fixing a loose or missing gas cap, replacing a spark plug, or clearing a check engine light. These repairs typically cost between $50 and $300 depending on the issue and the shop. If your vehicle has a serious emissions problem, a mechanic can run a more detailed diagnostic to pinpoint the cause.

Renewing your registration after a passing test

Once you have a passing test result, you must show it to renew your registration. You cannot renew online or by mail if a test is required in your area — you must visit a Colorado Division of Motor Vehicles (DMV) office in person or through an authorized third-party registration office (usually a local county clerk's office).

Bring your vehicle registration, proof of insurance, and your emissions test result sheet. The DMV will verify that the test passed and matches your vehicle's identification number, then process your registration renewal. Registration renewal costs vary by vehicle type and weight but typically range from $100 to $200 for a two-year renewal.

Your new registration is valid for two years from the date of renewal. Your next emissions test will be due two years later, in the same month. You will receive a renewal notice in the mail about 60 days before your registration expires, reminding you that a test is required.

What to do if you move or buy a vehicle

If you move from a testing area to a non-testing area in Colorado, you no longer need emissions testing. When you renew your registration, you can do it online or by mail without a test result. If you move from a non-testing area to a testing area, you will need a test before your next registration renewal.

If you buy a used vehicle from out of state and register it in Colorado for the first time, you must get an emissions test before you can complete registration, even if you live in a non-testing area. This is a one-time requirement for out-of-state vehicles. After that first test, you follow the normal two-year cycle for your area.

If you buy a vehicle from a Colorado dealer or private seller in a testing area, the seller may have already provided a recent test result. You can use that result for your registration as long as it is current and matches the vehicle's identification number. If the test is older than 30 days or does not match your vehicle, you will need a new test.

Cost breakdown and payment

The emissions test itself costs between $20 and $40 depending on the testing station. This fee is set by the individual shop, not by the state, so prices vary. You pay this fee at the time of testing, whether you pass or fail. If you fail and retest at the same station within the allowed window, there is no additional charge for the retest.

If you fail and choose to have repairs done, those costs are separate and depend entirely on what your vehicle needs. A straightforward fix like a gas cap replacement might cost $5 to $20. A sensor replacement might cost $100 to $300. A more complex repair could cost more. You are not required to have repairs done at the testing station — you can take your vehicle to any mechanic.

Registration renewal costs are separate from the test and are set by the state based on your vehicle's weight and type. A standard passenger vehicle typically costs $100 to $150 for a two-year renewal. Trucks and larger vehicles may cost more. You pay this fee at the DMV or county clerk's office when you renew your registration.

Frequently Asked Questions

What if I have a check engine light on?

A check engine light does not automatically mean you will fail the emissions test, but it may. The technician will scan your vehicle and see what triggered the light. If it is related to emissions, you may fail. If it is unrelated, you may still pass. You can have the light diagnosed before testing, or you can test first and see the results.

Can I test my vehicle before my registration expires?

Yes. You can test up to 90 days before your registration expires. The result is valid for 90 days, so if you test early, make sure the result will still be current when you renew your registration. Testing early can be useful if you want to address any failures before your registration important date.

What if the testing station made a mistake or I disagree with the result?

You can request a retest at the same station or a different station. If you believe the station made an error, contact the CDPHE directly at the phone number on their website. The state can review testing records and investigate complaints about station accuracy.

Do I need emissions testing if I have a hybrid or electric vehicle?

Hybrid vehicles registered in a testing area must test like any other vehicle. Electric vehicles are exempt from emissions testing statewide because they produce no tailpipe emissions. If you own an electric vehicle, you do not need a test regardless of where you live in Colorado.

What happens if I do not test and my registration expires?

You cannot legally drive a vehicle with an expired registration. If your registration expires and you have not tested, you must get a test and renew your registration before you can drive again. Driving with an expired registration can result in a traffic citation and fines.