Emissions testing, also known as a smog check, is required in many parts of the country. The procedure helps ensure your car emission control meets the policies of the Environmental Protection Agency (EPA) and state governments. Exactly how often your vehicle must be tested depends on the state or local government’s requirements. The same goes for which model year is exempt or subject to emissions testing.
There are two basic types of emissions tests: tailpipe and onboard diagnostics (OBD II). Which one your car must undergo depends on the requirements in your area and the age of your vehicle.
- With an OBD test, a scan tool is plugged into the vehicle’s diagnostic port. That allows the technician to communicate with the onboard computer to flag any emissions-related problems. OBD tests are only performed on the model year 1996 and newer vehicles.
- On the other hand, a tailpipe test requires inserting an exhaust gas analyzer into the car’s tailpipe. The analyzer measures the levels of hydrocarbons (HC) and carbon monoxide (CO), both of which are pollutants, as well as harmless carbon dioxide (CO2) and oxygen. Many locations also check levels of the pollutant oxides of nitrogen (NOx).
It’s worth considering that a visual inspection is part of the emissions test (both tailpipe and OBD) in most cases. During the examination, the technician checks to be sure the car’s emissions equipment is intact. Additional items, such as the gas cap, may be inspected as well.
Tips & Tricks for Passing an Emissions Test
The requirements for passing a tailpipe test are different from those for passing an OBD test. Therefore, each has a distinct set of preventative measures you should take before test day.
- Passing a tailpipe test
If a tailpipe test is required where you live, you can take a few steps to ensure a favorable outcome. While these measures won’t guarantee your car will pass, they will give you a leg up on test day.
- Warm-up your engine
Before getting your car tested, drive for at least 20 minutes to warm it up. You should schedule an appointment with the testing center to be accommodated while your engine is still warm. Doing so will help ensure both the engine and catalytic converter are at the optimum temperature for testing.
- Make sure your car is up-to-date on routine service.
Following the manufacturer’s recommended maintenance schedule helps keep your vehicle running at its best. The plan includes procedures such as fluid changes, filter replacements, and tune-ups, all of which can affect emissions test results.
So, before you visit the emissions station, be sure your car is up-to-date on routine service. An outline of the service schedule is located in your owner’s manual.
- Fix any known engine-related problems
If your engine is working rough, stalling, or exhibiting any other problems, you’ll want to fix the issues before getting an emissions test. The reason being, engine-related issues often lead to an increase in tailpipe emissions.
- Make sure the Engine light is off.
The emissions test will not pass with an illuminated check engine light. If the light is on, you’ll need to get the problem that triggered it before testing.
- Passing an OBD test
You’re in luck if your location only requires an OBD test. There are just a couple of things you’ll need to check before heading to the emissions station.
- Ensure that the “Check Engine” light is off
Once again, your car will not pass an emissions test if your “Check Engine” light is illuminated. Make sure to address this issue and resolve the triggered problem before you go in for testing.
- Ensure all the monitors have run
Your car’s computer runs self-tests known as “monitors” on emissions-related systems. During an emissions test, a smog technician will check that all (or nearly all, depending on local requirements) of these monitors have “run” successfully.
The monitors are reset whenever the battery is disconnected. Clearing diagnostic trouble codes (DTCs) from the computer’s memory also reset the monitors. If either has been done to your car recently, you’ll want to be sure the monitors have run before emissions testing. If they have not, your vehicle will be given a “not ready” test result, rather than passing or failing.
You can check whether the monitors have run using a scan tool or code reader if you have one. Otherwise, you’ll want to drive the vehicle at various speeds (both on city streets and the highway) for an extended period. This way, there is a better possibility of being ready for emissions.
How long does a smog check take?
A smog check typically takes more or less 30 minutes. It can depend on the number of vehicles in line and whether you could schedule your vehicle for an appointment ahead of time.
What causes a failed emissions test?
Have a professional troubleshoot your car if it fails the emissions test.
There are countless reasons why your car could fail an emissions test that requires a professional diagnosis. Here are some examples of what a technician might find during troubleshooting:
- Engine and transmission problems
Problems with either the engine or transmission can lead to an increase in tailpipe emissions and an illuminated “Check Engine” light. The result is a failed emissions test.
- Emissions equipment failure
Modern cars have an array of emissions equipment onboard. A few examples include the catalytic converter, exhaust gas recirculation system, an evaporative emissions system. Problems with such equipment can easily cause your car to fail an emissions test. You can visit The Auto Parts Shop and place an order for affordable automobiles.
- Module and sensor issues
Today’s vehicles contain an expansive collection of computers (referred to as modules and sensors). Issues with these electronics, their wiring or data network, can lead to a failed emissions test.
- Air/fuel delivery problems
Your car’s engine requires a precise mixture of both air and fuel to run correctly. If either of these ingredients is thrown out of whack, there’s a good chance your car will fail its emissions test.
- Ignition system concerns
The ignition system contains the components that ignite the air/fuel mixture inside the engine. A complication with any of these parts can create an engine misfire that leads to a failed emissions test.
If you cannot afford the necessary emissions-related repairs, some states offer financial assistance to help out. Investigate with your local government to figure out what’s available in your area.