Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. How Is the OBD Used During a State-Required Inspection?

How Is the OBD Used During a State-Required Inspection?

obd test

If you live in an area that requires emissions testing each year, you’ll be required to go through a two-part test. The testing facility will do two things: they’ll measure the gases in your exhaust via a tailpipe test, and they’ll check your OBD (On-Board Diagnostics) system. What role does the OBD system play here? Why is a check of the OBD system needed if the facility conducts a tailpipe test?

Two reasons for a two-part test

There’s actually a very simple reason why the testing facility in your area will require an OBD test in addition to a tailpipe test. Contrary to popular belief, the OBD system does not measure gases produced other than oxygen. A tailpipe test is needed to analyze the different gases being produced and ensure that your car is within limits set by the government.

The second reason is tied to the first. A tailpipe test only checks for gases in your emissions. It can’t assess the health of your emissions control components. That’s what the OBD system does – it monitors your emissions equipment, such as the catalytic converter, oxygen sensor, and EGR valve. When a problem with one of these components occurs, the car’s computer sets a temporary code. If the problem is detected more than once, the computer turns on the Check Engine Light.

What an OBD system does

The OBD system does more than just light up when a part has failed. It’s able to detect progressive deterioration of your car’s emissions control components. This helps avoid potentially serious damage to the car, but also ensures that you’re able to replace failed emissions control equipment before the car begins creating serious pollution.

If the Check Engine Light is on in your dash, your car will not pass the emissions test, as there is a problem that will need to be repaired first. However, your car may not pass testing even if the Check Engine Light is not on, particularly if you fail the gas cap pressure test.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How to Buy Fuel Treatments
Adding a fuel additive to your gas tank when you fill up is one way to clean vital engine parts of deposits, improve the performance of your engine,...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...

Related questions

Q: Are Code Readers and Scan Tools Different?

There are differences and similarities between code readers and scan tools. With the advent of the vehicle on board diagnostic system (OBD) there have been many different makers of scan tools and code readers. The code readers were the first...

Q: my 04 eclipse wont start no spark from plugs or anything i was driving and it just shut off i replaced timing belt crank sensor an

In the event that diagnostic trouble codes have been set by the PCM, downloading those codes will greatly narrow the possibilities that you have to consider. No spark could be due to bad grounds (possibly in the plenum area; see...

Q: Can't read OBD code with my scanner.

These aftermarket type scanners may not access every vehicle out there. When you get a cannot communicate issue this is most likely the OBD adapter and the vehicle may be incompatible or the vehicle has problems. You would need to...