What is an emissions test?
A car emissions test, or e-check, checks the emissions of your vehicle to make sure that the greenhouse gases and pollutants released by your car fall within your state's legal limits. Car emissions testing is often conducted by connecting your car to a testing system through your car's onboard diagnostics port (OBD2 port). For older vehicles that don't have this option, testing sites will put your car on a dynamometer (essentially a treadmill for your car) and attach a sensor to your tailpipe.
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What do they check for during an emissions test?
Emissions tests may check the levels of any or all the following in your exhaust:
- Benzene
- Carbon dioxide
- Carbon monoxide
- Hydrocarbons
- Nitrogen oxides
- Oxygen
- Sulfur dioxide
Some of these emissions are checked due to their impact on human health, while others are examined due to their impact on the environment.
What states require vehicle emissions testing?
30+ states require emissions testing for cars, and exact rules vary widely by state. Some states only require testing in certain areas of the state, including certain counties and metropolitan areas. Check with your local department or bureau of motor vehicles (DMV or BMV) for the exact rules in your area.
California has implemented the strictest laws around emissions testing, and many other states have used California as a model for their emissions testing.
How do I find out if my car needs an emissions test?
When an emissions test is required, it's usually tied to your vehicle registration process. When you need to renew your vehicle registration, part of that renewal notification will usually include a reminder that you're due for an emissions test. How often your vehicle needs an emissions test will vary by state, county, or city. Check with your state's DMV or BMV to see how often you need to test your vehicle or if your car is exempt from emissions testing.
How long is an emissions test good for?
The exact timeframe varies by state, but an emissions test will typically last one to two years. Contact your DMV or BMV to find out how long an e-check is good for in your state.
What happens if your car fails its emissions test?
A failed emissions test usually means your car needs to be serviced or repaired before you can renew your registration and drive it legally. You may have a grace period where you can legally drive the car before retaking the emissions test.
What causes a car to fail an emissions test?
A vehicle may fail an emissions test for several reasons, including:
Your car battery has been disconnected recently
If your car battery has been disconnected within the last couple of weeks — during repairs, for example — the on-board diagnostics (OBD) system may not have enough information stored in its memory for inspection purposes. You may need to return in a week or so for another test.
Data Link Connector (DLC) issues
Also known as an on-board diagnostics port (OBD2 port), this is how your car connects to the inspector's testing system. Problems with the port or the connection can cause a test failure.
Your "check engine light" came on
It mostly appears due to exhaust system problems, but not always. Issues with the battery or its cables can trigger it, as well as third-party alarm systems.
Actual test failure
In this case, your vehicle inspection report will contain a list of one or more diagnostic trouble codes (DTCs). You'll need to take the report to a qualified mechanic, who can tell you which services or repairs are needed.
Exhaust systems issues
The exhaust system routes the burnt gases from the engine out through your exhaust pipe. A catalytic converter, which is part of this system, transforms some of those gases into water and carbon dioxide. Issues with a catalytic converter can cause an emissions test failure.
Other issues that could cause an emissions test failure include problems with your ignition, fuel injection and air injection systems, and faulty sensors. It's important to get these issues addressed and fixed as soon as possible.
What if you fail an emissions test twice?
If your car fails an emissions test more than once, you may have a few options outside of continually getting it repaired:
- Economic hardship: In some cases, you may apply for an emissions testing extension or waiver if you're unable to afford the necessary repairs.
- General repair cost limits: If you've already spent a certain amount of money on repairs that were intended to address a failed emissions test and the issue isn't fully resolved, you may be able to apply for a waiver.
- Limits on specific cars: Some DMVs or BMVs may grant you a waiver if the repair cost would be more than the maximum amount allowed for your car's age, make, and model.
Is there any impact to insurance if a car fails its emissions test?
If your car fails its emissions tests and you can't register your car or renew its registration, you likely won't qualify for insurance coverage — that's because it would be illegal to continue driving the vehicle. Emissions checks are typically required to renew your car's registration, and your car must be registered to be insured and legally driven.
To avoid any impact to your insurance, address your cars emissions issues, and get it re-checked so you can maintain your car's registration.
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