How Texas emissions testing works

Texas requires emissions testing in 31 counties in the Dallas-Fort Worth, Houston, Austin, and San Antonio areas. If you live in one of these counties, you must pass an emissions test every two years (or every year if your vehicle is a heavy-duty diesel truck). The test measures what comes out of your tailpipe — carbon monoxide, nitrogen oxides, and particulate matter — to may support your vehicle meets state air quality standards.

You can take the test at any licensed emissions testing facility in your county. These are private businesses — repair shops, quick-lube places, tire shops — that have been certified by the Texas Commission on Environmental Quality (TCEQ) to run the test. The test itself takes about 10 to 15 minutes and costs between $15 and $35, depending on the facility.

Your vehicle must pass the test before you can renew your vehicle registration. If you fail, you have 30 days to fix the problem and retest at no additional charge at the same facility. If you fix the vehicle at a different shop, you will pay the testing fee again.

Key Takeaways

  • Texas emissions testing is required every two years in 31 counties, primarily around Dallas-Fort Worth, Houston, Austin, and San Antonio.
  • You can take the test at any licensed private facility in your county, and the test costs $15 to $35 and takes about 10 to 15 minutes.
  • If you fail, you have 30 days to repair your vehicle and retest for free at the same facility where you failed.
  • You cannot renew your vehicle registration without a passing emissions test result in a required county.

Which Texas counties require emissions testing

The 31 counties that require emissions testing are concentrated in four metropolitan areas. In the Dallas-Fort Worth region: Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant counties. In the Houston area: Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller counties. In the Austin area: Bastrop, Caldwell, Hays, Travis, and Williamson counties. In the San Antonio area: Bexar, Comal, Guadalupe, and Wilson counties.

If you live outside these 31 counties, you do not need an emissions test to register your vehicle. You can check whether your county is on the list by entering your county name on the TCEQ website or calling your county tax assessor-collector's office.

What happens if you fail the emissions test

A failed test does not prevent you from driving your vehicle — it only blocks registration renewal. You have 30 days from the test date to repair the vehicle and retest. The retest is free if you return to the same facility where you failed.

Common reasons for failure include a faulty oxygen sensor, a loose or missing gas cap, a malfunctioning catalytic converter, or an engine that is running too rich (burning too much fuel). A repair shop can often diagnose the problem during the test or when ready after. If you are unsure what to fix, ask the testing facility what the test results showed — they must provide you with a detailed report.

If you repair the vehicle at a different facility than where you tested, you will pay the testing fee again when you retest. Some repair shops offer free retesting if they do the repair work, so it is worth asking before you leave.

Finding a licensed emissions testing facility

The TCEQ maintains a searchable database of all licensed testing facilities on its website. You can search by county and city to find facilities near you, along with their hours and phone numbers. Many facilities accept walk-ins, but calling ahead to confirm hours and wait times is a good idea, especially during busy seasons (late summer and fall).

You will need to bring your vehicle keys and a valid photo ID. Some facilities may ask for your vehicle registration, though it is not always required. Bring your vehicle's odometer reading if you have it, as some facilities record mileage.

Emissions testing for older and specialty vehicles

Vehicles that are 1996 or newer must pass the standard on-board diagnostic (OBD) test, which reads data from your vehicle's computer. Vehicles from 1995 and older may be exempt from testing in some counties, or may be subject to a different test. Check with your county tax assessor-collector or the TCEQ to confirm the rules for your vehicle's model year.

Diesel vehicles, motorcycles, and vehicles with recent engine modifications may have different testing requirements. If your vehicle is a heavy-duty diesel truck, you may be required to test every year instead of every two years. Call the TCEQ or your county assessor-collector to confirm what applies to your specific vehicle.

Emissions testing and vehicle registration renewal

You must have a passing emissions test result before you can renew your registration. When you renew online or in person at your county tax assessor-collector's office, the system will check whether a passing test result is on file for your vehicle. If no result is found, your registration renewal will be blocked.

The test result is valid for 120 days from the test date. Plan to test within that window before your registration expires. If your registration has already expired, you can still take the emissions test and then renew your registration, but you may face late fees.

Frequently Asked Questions

Can I take the emissions test before my registration expires?

Yes. The test result is valid for 120 days, so you can test up to four months before your registration expires. This gives you time to fix any problems and retest if needed.

What if I move to a county that does not require emissions testing?

Once you establish residency in a non-testing county, you no longer need to pass an emissions test to register your vehicle there. You will need to update your address with your county tax assessor-collector when you renew your registration.

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

No, but the seller may need one to transfer the title. Check with your county tax assessor-collector about the specific rules for your situation. The new owner will need a passing test before the first registration renewal in their name.

What if the testing facility says my vehicle cannot be tested?

This is rare but can happen if your vehicle is not in safe operating condition (for example, the check engine light is on and the computer will not communicate with the test equipment). Ask the facility what the specific problem is and whether it can be fixed before retesting.

How much does an emissions test cost?

The cost ranges from $15 to $35 depending on the facility. The TCEQ does not set a fixed price, so you can call ahead to compare costs in your area if price matters to you.