Find Emissions Testing &
Smog Check Locations Near You

Whether you drive a daily commuter, a diesel truck, a hybrid, or you are moving to a new state, you will know exactly what to expect and how to stay legal.

What Is an Emissions Test or Smog Check?

An emissions test (often called a smog check) measures the pollution your vehicle puts into the air and checks that its emissions control systems are working correctly.

Depending on your state and vehicle, a test may include:

• An OBD-II scan for most 1996 and newer vehicles
• A tailpipe test while the engine idles or runs on a dynamometer
• A gas cap or evaporative system test
• A visual inspection for missing or tampered emissions equipment

The goal is to keep air quality within federal Clean Air Act limits.

Do I Even Need an Emissions Test?

You only need a smog check if your state requires it for your vehicle and registration address.

You are more likely to need testing if you live in or near a major metro area with air quality issues, if your state is known for testing (California, Arizona, Colorado, Texas, New York, etc.), or if your vehicle is a gasoline or light duty diesel from middle model years.

You are often exempt if your vehicle is brand new (within the first few model years), if it is very old, classic, or antique and registered as such, if it is fully electric, or if you live in a state or county with no emissions program.

To see what applies to you, pick your state in the directory and check the current rules for 2025.

Types of Emissions Tests

Most programs use one or more of these:

OBD-II test. The technician plugs a scanner into your OBD port and reads fault codes, readiness monitors, and the status of your check engine light. This is now the most common test.

Dynamometer or loaded test. Your car runs on rollers while equipment measures exhaust under simulated driving conditions.

Idle or two speed idle test. A probe in the tailpipe measures emissions while the car idles and sometimes at a slightly raised RPM.

Diesel opacity test. Measures how much smoke is in the exhaust from diesel engines.

You do not choose the method. Your state and vehicle type decide it for you.

How to Prepare for an Emissions Test

A little prep can save you a lot of pain. Before you go:

Make sure the check engine light is off. If it is on, the car will almost certainly fail an OBD based test. Fix obvious issues like a loose or cracked gas cap first.

Drive the car normally for a few days. After a battery disconnect, major repair, or code clear, your OBD readiness monitors need time and driving cycles to reset. Short trips only can keep monitors incomplete and trigger an automatic fail.

Do basic maintenance. Check oil level and condition. Make sure there are no major misfires, rough idle, or obvious fuel or air leaks. Ensure tires are properly inflated if you will be on a dyno.

Warm up the engine. Drive at least 10 to 15 minutes before testing so the engine, catalytic converter, and O2 sensors are at operating temperature.

Bring the right documents. Registration or renewal notice, proof of insurance if your state requires it, and photo ID.

What Happens During the Test

While the exact steps vary, a typical visit looks like this:

Check in. You pull into the lane or bay, provide registration and ID, and pay the fee unless it is billed differently in your state.

Vehicle verification. The technician confirms your VIN, license plate, and sometimes mileage.

Inspection and testing. For 1996 and newer vehicles this means an OBD-II scan. For older vehicles it is a tailpipe test on a dyno or at idle. There may also be a gas cap or evaporative system check and a quick visual look for missing catalytic converters or obvious tampering.

Result printout. You receive a Vehicle Inspection Report showing pass or fail and any codes or readings. In many states, results are also sent directly to the DMV system.

If you pass, you are done. Use the result to complete your registration if it is not applied automatically.

If Your Vehicle Fails the Emissions Test

Failing is not the end of the world, but you need a plan:

Read the failure report carefully. Look at the specific codes or reasons such as P0420 catalytic converter efficiency, EVAP leak, or failed readiness monitor.

Get a proper diagnosis. For anything beyond loose gas cap, a qualified shop or emissions certified repair facility is worth it. Do not just clear codes and retest. Most programs can detect this and you will still fail.

Complete repairs and keep receipts. Many states offer repair waivers or cost cap programs if you have spent over a certain amount trying to fix the issue. Receipts, parts lists, and shop invoices are often required.

Retest within the allowed window. Most programs give a free or discounted retest if you return within a set number of days.

Your state page in this directory will outline any waivers, hardship programs, or repair assistance that might be available.

Special Rules for EVs, Hybrids, and Diesels

Electric vehicles. EVs do not have tailpipe emissions, so they are generally fully exempt from smog checks.

Hybrid vehicles. Many states treat hybrids like normal gasoline cars for OBD-II testing. Some programs exempt the newest model years. Your state rules will say which.

Diesel vehicles. Light duty diesels may face OBD, opacity, or dyno tests. Heavy duty diesels often fall under different weight class or safety and commercial inspection rules.

Always check your state page for fuel type specific requirements before you schedule a test.

Quick Checklist Before You Go

Use this fast checklist on test day:

• Check engine light is off
• No recent battery disconnect or code clear within last few days
• Vehicle has been driven normally and is fully warmed up
• Gas cap is tight and not cracked
• Basic maintenance is up to date
• You have registration or renewal notice and ID
• You know where the nearest approved testing station is

If you follow these steps, emissions testing becomes a quick errand instead of a stressful unknown. If anything goes sideways, your state page will point you to the exact rules, locations, and options you have.