We Buy All Cars, Running or Not!

Everything You Need to Know About Getting Your Smog Checked Before Selling Your Car

Getting Your Smog Checked Before Selling Your Car

Most states require a smog test or a new smog certificate before selling a car. Smog check requirements vary per state. The vehicle smog inspection is governed by each state individually. This article includes general guidelines on how to pass smog tests and explains some state-specific requirements on emissions tests you should know when selling your vehicle. Read on to find out everything you need to know about getting your smog checked before selling your car.

⚠️ If It's Broken, Don't Fix It - Get Paid Cash for Your Vehicle ⚠️

Does the seller of a car have to smog it?

You, the seller as the original, is responsible for the emission test or the smog check according to Section 24007 (b)(2) of the California Vehicle Code. You are responsible for providing a valid smog certificate before or during the sale of a car.

Can you sell a car that hasn't passed smog?

Selling a car without an emission test or smog check is difficult to do in most states that require this test. You will need to get permission from your state’s Department of Motor Vehicles if you want to sell a car without a smog check. Or you may need to make an entirely separate agreement or contract stating that both parties agreed that the car may not be able to pass a smog test or inspection. 


To check your state’s emission requirements, click here


Gentleman's Agreement in Writing

Some states that require emissions testing will let you sell a car that may not be able to pass a smog check given that the buyer states that he or she is aware of it and does so in writing. This document should be separate from any bill of sale or other document connected with the sale.

When selling a car that is unable to pass a smog test, and the buyer agrees in writing, you should get this document notarized. In some states, it is required for you to submit this document to the DMV when reporting the sale. If you have questions or concerns about the procedure required, consult the appropriate agency in your state.

Planned Non-Operation Method

Some states do not allow the sale of a car without an emission test even if there is a written, notarized agreement between you, the seller, and the buyer. In these states, you are required to report to the DMV that the car will not be used on state roads and highways. This is usually called Planned Non-Operation.

It is legal to sell a car that is in Planned Non-Operation status, but the buyer will not be able to operate the vehicle legally on state roads and highways until they get the car inspected and get a clean bill of health — a smog certificate. Afterward, the buyer can apply to the DMV to have the Planned Non-Operation status lifted. The DMV typically charges a fee for you to remove this status. 


Retire the Vehicle and Get Paid

To keep pollution-causing vehicles away from the highway, some states give you the option to retire your car with the Department Motor of Vehicles. States that offer this, in general, will give you a particular amount for your old car and then dispose of it properly. The amount you will get for your car from the state will depend on where you live. Most states give between $250 and $500 for old cars. 


If your state does not make this option available to car owners, you can still get rid of your old car by selling it to a junk salvage yard or junk car buyers. In many cases, the amount you get from the salvage yard will be on par with the amount given by states that have vehicle retirement programs.

How long should I drive my car before a smog check?

You should drive your car for at least 20 minutes before subjecting it to a smog test. To make sure your car conforms to vehicle laws, it is important to pass a smog test. On top of that, it’s better for the environment and for the performance of your car when it follows the state smog standards. 


What many people don’t know is that there are numerous factors that can affect the result of a smog test. Moreso in older cars or cars that have not been used for a long time. Here are six factors that could significantly affect the outcome of your smog test.


  1. Repairs needed – If your vehicle requires immediate repairs, it is not advisable to subject it to a smog check. There is a high probability you will fail the emission test if major repairs are needed. You should complete major engine repairs first before bringing your vehicle in for the emission test. You will likely pass the test by then. 


  1. Recent battery replacement or disconnection – There’s a chance that your car’s internal test monitors will be deleted when you replaced or disconnected the car’s battery. The monitored information is needed by the smog testing facility for your car to complete and pass an emission test. 


If you have just replaced or disconnected your battery, you must wait a week or about 100 miles before you subject your car to a smog check. This is to make sure that your vehicle has the right data to complete the test.


  1. Cold engine – It is not ideal for your car to undergo a smog check when it has a cold engine that’s only recently started. You should drive your vehicle for at least 20 minutes before taking it in for a smog inspection. This is important so that your engine is warmed and has reached the correct fuel mixture and combustion levels. 


  1. Oil Change – Contaminated or dirty engine oils can also have a negative effect on your car’s smog test. The engine is made to take in some fumes that are coming from various oil compartments. These fumes then combine and become part of the combustion of the engine. If your oil is due for a change, it could cause your car to fail a smog inspection.


  1. Check Engine Light is on – If your check engine light is illuminating, better not subject your car to a smog inspection. Chances are your car will fail the smog test. If your check engine list continues to be on during the smog check, you might automatically fail. According to California state law, mechanics can’t refuse the test based on having a check engine light on. 

  1. Tire inflation – During a smog inspection, the technician usually drives your car on a dynamometer to get various readings. Correct tire pressure is necessary to make sure that the vehicle can be driven properly and in a stable manner during the test. If your tires are incorrectly inflated, they could affect the test result, particularly for borderline results.

What if my car fails the smog test?


If you fail the smog test, the technician typically provides a form indicating the reason your car failed and its emission levels. Show this form to your mechanic for them to determine if they know how to fix the issue.


If there is still trouble finding the issue, let your mechanic conduct a smoke test which forces smoke into the vehicle’s evaporative system to locate any leaks in the rubber houses leading to and from the engine. You might find a cracked rubber hose that is the culprit of the problem. It may cause you around $140 to fix the problem. 


If it is the first time that your car failed, it is recommended to retest it at a fix and repair station instead of one that only does testing. The technicians in these stations are usually experts in emissions systems repairs, thus you need not drive back and forth between garages and testing stations.

Lastly, if you fail the test and you don’t have the money to do the necessary repairs, you might qualify for financial assistance. For instance, in California, the Consumer Assistance Program gives up to $500 to eligible car owners for emissions-related repairs.


But prevention is always better than cure so it is best to do everything you can to make sure you don’t fail the emission test. Here are things you can do to make sure your car will pass the smog test:

Be proactive

Once you get a registration renewal notice calling for a smog test, mark the date and start preparing. This way, if something goes wrong, you have lots of time to address issues. Pay registration fees early to avoid spending extra on late charges, though you won’t get your registration until the test is complete.


Most states require smog tests every 2 years, or before selling a vehicle, but requirements, costs, and testing methods vary. For instance, some stations perform a dynamometer test, particularly for older vehicles, allowing the wheels to turn and simulate driving conditions. Read your notice to know whether you need to bring your car to a specific type of station.

For example, some stations use a dynamometer test, particularly for older cars, which allows the wheels to turn and simulate driving conditions. So check your notice to see whether you need to bring your vehicle to a specific type of station.

Conduct necessary maintenance

Check your car owner’s manual to know the required maintenance at different mileage intervals. Perform any necessary service items before having your car tested.

Of course, you need not wait for a smog test to do routine maintenance. Have oil changes and tune-ups regularly and be sure your tires are properly inflated. This way, when it’s time for a smog test you’ll be ready.

A fuel injector cleaner may also help. It can get rid of clean carbon deposits from your engine and reduce emissions. You might fail an emission test just cause you failed to change spark plugs. 

Clear your check engine light

If your check engine light illuminates, you have an issue that needs immediate attention.  Problems that cause the check engine light to be on could require inexpensive repairs, such as loose or a damaged gas cap, or it might mean more serious repairs. Find out and repair what’s causing your check engine light to turn on.

But even after everything’s been fixed and it clears the check engine light, you need to drive until the car’s computer verifies that all operating systems are working as it should be. That’s why the next step is necessary.

Precheck your car

There are shops that offer free diagnostic analysis. You can use it to pretest your vehicle for smog-check readiness. These tests aren’t just for smog tests, they’ll also let you know of the remaining problems. This is particularly helpful if you’ve just fixed the problems or if you own an older car you’re worried might fail.

What makes you fail a smog test?

If your vehicle fails the smog test, you must do the required repairs before you can renew your state auto registration or sell your car. Because there are many components that make up the engine’s emissions system, there are several possible causes. Some repairs are easy to do, while others mean more serious engine problems.


  1. Leaking gas cap – A gas tank that’s worn, cracked, or improperly sealing could cause increased emissions.
  2. Dirty air filter – A filter that hasn’t been replaced when it’s already due could be the reason you failed your smog test. This is an easy fix.
  3. Defective ignition system – Defective or old spark plugs or wires are usually the culprits. When your car’s ignition system runs inefficiently, it releases more hydrocarbons.
  4. Catalytic converter malfunction – Its job is to turn the carbon monoxide, nitrogen oxide, and hydrocarbons released by the engine into water and carbon dioxide. Any issue with this part could cause you to fail the smog test. Catalytic converters are made with expensive materials so fixing them is usually costly.
  5. An issue with the evaporative emission control system – This system keeps your car from releasing vapors from raw gasoline into the atmosphere. More testing will determine if the issue is with the vents, purge valves, vacuum hoses, or elsewhere. 


Selling a car without a smog test is hard to do in most states that require it. You will need to get permission from your state’s DMV, or you may need to make an entirely separate agreement or contract stating that both parties agreed that the car may fail a smog inspection. And even if you are allowed to sell it, you should also report to the DMV that is in Planned Non-Operation status. But you should not be worried so much because it is easy to pass a smog test as long as you are prepared for it. 


© 2022 Cash Cars Buyer. All Rights Reserved. Terms & Conditions | Privacy Policy | Sitemap