What Denver requires for diesel vehicles

Denver requires diesel vehicles to pass an emissions test every two years as part of the state's vehicle inspection program. The test measures particulate matter, nitrogen oxides, and opacity — how much visible smoke comes from the tailpipe. Diesel vehicles that fail must be repaired and retested before you can renew your registration.

The emissions test is separate from the safety inspection, though both happen at the same testing station. You'll pay one fee for both tests together, typically between $20 and $30 depending on the station. The test takes about 15 minutes.

Colorado's diesel standards are stricter than federal minimums. Vehicles manufactured after 1996 must meet Tier 2 standards; older vehicles have different limits. If your diesel vehicle was built before 1996, ask the testing station which standard applies to your model year before you go in.

Key Takeaways

  • Denver diesel vehicles need an emissions test every two years, and the test measures particulate matter, nitrogen oxides, and visible smoke.
  • You can get tested at any Colorado Department of Revenue-approved station in the Denver area, and the test 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.
  • Diesel vehicles built before 1996 follow different emission standards than newer ones, so confirm which applies to your vehicle before testing.
  • Repairs covered under the Repair information Program may be free or low-cost if your vehicle fails and you meet income limits.

Where to get tested in the Denver area

You can be tested at any Colorado Department of Revenue-approved emissions testing station. The state maintains a searchable list on its website where you can filter by county and find stations near you with their hours and phone numbers. Most stations are open weekdays and some offer Saturday hours.

Private repair shops, tire shops, and dedicated emissions testing centers all perform the test. You do not have to test where you plan to get repairs done if your vehicle fails — you can test at one station and take the vehicle elsewhere for work. However, retesting must happen at the same station where you failed, within 60 days.

Bring your vehicle registration and a photo ID. The technician will plug a diagnostic scanner into your vehicle and run the tailpipe test. You'll get your results on the spot.

What happens if your diesel vehicle fails

A failed emissions test does not automatically mean your vehicle is unsafe or that you must scrap it. You have 60 days from the test date to have repairs made and return for a retest at the same station. The retest is free if you return within that window.

Common reasons diesel vehicles fail include a faulty oxygen sensor, a malfunctioning diesel particulate filter, or an engine control module problem. A technician can read the diagnostic codes to narrow down what needs fixing. Repair costs vary widely depending on the problem — some fixes cost under $100, while others may run several hundred dollars.

If you cannot afford repairs, Colorado's Repair information Program may cover some or all of the cost. The program is income-based and covers repairs up to a set dollar amount. You must be denied the repair information before you can claim a hardship exemption, which temporarily postpones the requirement to pass.

The Repair information Program for diesel vehicles

The Repair information Program covers emissions-related repairs for vehicles that fail testing. You must own the vehicle, live in Colorado, and meet income limits based on household size. The program pays the repair shop directly, not you.

To use the program, you first take your failed emissions test results to a participating repair shop. The shop submits a repair estimate to the program. If the estimate is approved and within the program's dollar limit, the program authorizes the repair and pays the shop. You pay any amount over the program's limit.

Not all repair shops participate. The state website lists participating shops by county. Call ahead to confirm they work with the program and can handle your vehicle's specific problem. Turnaround time for approval varies but typically takes one to two weeks.

Hardship exemptions and waivers

If your diesel vehicle fails and repairs cost more than the Repair information Program covers, or if you do not meet the program's income limits, you may be able to get a hardship waiver. The waiver temporarily postpones the requirement to pass emissions testing, usually for one year.

To get a waiver, you must first be denied the Repair information Program. You then submit a hardship process to the Colorado Department of Revenue with documentation of the repair cost and your financial situation. The state reviews the process and notifies you of approval or denial.

A waiver is not permanent. When it expires, you must either pass the test or explore for another waiver. If you receive multiple waivers in a row, the state may require you to scrap the vehicle or remove it from Colorado registration.

Diesel vehicles older than 1996

Diesel vehicles built before 1996 follow different emission standards than newer ones and are tested differently. Some older diesel vehicles are exempt from testing altogether depending on their model year and weight. Before you schedule a test, confirm with the testing station whether your vehicle must be tested.

If your pre-1996 diesel vehicle does require testing, the standards are less strict than for newer vehicles. However, the test procedure is the same — a tailpipe test measuring particulate matter and opacity. Ask the station which standard applies to your specific model year so you understand what the pass threshold is.

Older diesel vehicles are more likely to fail because emission control technology was less advanced. If your vehicle fails, the same repair information and hardship waiver options are available.

Preparing your diesel vehicle for testing

Before you go in for a test, make sure your vehicle's engine is in reasonable condition. Change the oil and oil filter if they are overdue — dirty oil can affect emissions readings. Check that your fuel cap seals properly and that there are no obvious leaks under the vehicle.

Warm up the engine for a few minutes before the test. A cold engine can produce higher emissions readings. If your check engine light is on, have the codes read before testing — some codes will cause an automatic fail, and knowing what they are beforehand lets you decide whether to repair first or test and see the results.

Bring your registration and ID. Some stations require an appointment; others take walk-ins. Call ahead to confirm hours and whether you need to book a time slot.

Frequently Asked Questions

Can I drive my diesel vehicle if it fails emissions?

Yes, you can drive it while you arrange repairs. You have 60 days to get the vehicle fixed and retested. However, you cannot renew your registration until the vehicle passes. If your registration expires before you retest, you cannot legally drive the vehicle on public roads.

What if I move out of Denver but still own a diesel vehicle registered here?

If you move to another state, you must transfer your registration to that state. If you move to another Colorado county, your vehicle still must pass Denver's emissions standards if you keep it registered in Denver. Check with the new county's requirements if you plan to re-register there.

Do diesel trucks have different emission standards than diesel cars?

Diesel trucks and cars follow the same Colorado emission standards. However, heavy-duty diesel trucks over a certain weight may have different testing procedures or exemptions. Ask the testing station whether your truck's weight class affects which standard applies.

How long does a retest take after repairs?

The retest itself takes about 15 minutes, the same as the initial test. You should schedule an appointment or arrive early to avoid a wait. Results are available when ready after the test.

What if the repair shop says the problem cannot be fixed?

Some diesel vehicles reach a point where emissions-related repairs are not practical. If a shop tells you the vehicle cannot be repaired to pass, get a second opinion from another shop. If multiple shops confirm the vehicle cannot pass, you may be able to get a hardship waiver or explore whether the vehicle qualifies for a scrappage program if one is available in your area.