Smog Check Failed: 5 Things You Can Do If Your Car Won’t Pass Smog Program

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Edgar Moulton.


Edgar Moulton. Car Expert

Table of contents

If you have a car that has recently failed its smog test, read on to see why that may be and if it’s possible to repair. If not, see what options you have for selling it legally and for the most money. 

What Happens If Your Car Fails an Emissions Test

Currently, 33 of the 50 states in the United States require a smog test. Among these 33 states, there are different levels of strictness for what means passing a smog test and what means failing one. Even among the same states, certain districts require smog tests while others don’t. 

So what happens if your car fails an emissions test? If you take your car to an emissions test center and receive a failed smog test, you won’t be able to register your car. Obviously, it’s illegal to drive around without valid registration, so don’t do that. Lucky for you, there are options for fixing whatever it is that is causing a smog test failure.

5 Reasons a Car Won’t Pass Smog Program

Nearly ten percent of all cars that take a smog test will fail them, so if you’re part of that ten percent, you’re not alone. There are a few common causes that will result in a smog check failure. Let’s have a look at them.

  • A Damaged Oxygen Sensor. A gasoline combustion engine works by combining oxygen and fuel to create an explosion within the cylinder. When the oxygen sensor is faulty or failing, it won’t input the correct fuel to oxygen ratio. This most often causes the car to use more gasoline than is usually required. More gasoline being used means greater emissions, which may mean a car that’s not passing smog. 
  • A Failed Evaporative Emission Control System. The Evaporative Emission Control System (more commonly referred to as EVAP) works in tandem with the fuel tank. Its purpose is to absorb gasoline vapors that evaporate from the gasoline in the fuel tank. When the EVAP doesn’t do its job correctly, gasoline vapors are being released into the atmosphere. If you’ve ever seen the mirage-like waves coming up from your fuel tank when you fill it with gasoline, that’s what is constantly happening when your EVAP doesn’t do its job.
  • Improper Fuel Mixture. Like we said in point number 1, your engine requires the correct ratio of fuel and air entering the cylinders at all times to run efficiently. Sometimes, a car can run too “rich,” meaning there is more fuel entering than required for the amount of air entering. When this happens, your vehicle will use more fuel than needed, and the smog check will notice this, resulting in a car that can’t pass emissions. This can happen from any number of things, ranging from your fuel injectors being in bad condition to a clogged air filter. 
  • Faulty ignition system. The ignition system in one’s car is combined of numerous parts and can be somewhat complicated. From improper ignition timing to defective components — if your ignition system is why your car won’t pass a smog program, it may be costly to repair
  • Defective Catalytic Converter. The catalytic converter (more commonly referred to as CAT) takes any leftover fuel and air not properly burned during the combustion process within the cylinder and burns it off more thoroughly so that the engine thoroughly burns off any fuel and emits less harmful emissions from your exhaust. The only way to test if this is what is causing your failed smog test is an expensive diagnostic tool called an exhaust gas analyzer. 

Those are the top 5 reasons why your car may have failed its smog test. 

How to Get Your Car to Pass Smog

First, if your car didn’t pass smog test, it’s not the end of the world. Strangely enough, it may even be a blessing in disguise. If your car got a “smog check failed” certificate, it means your car isn’t running as optimally as it should be. 

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As you can see in our Cash For Clunkers article, one of the main goals of the federal government regulating emissions is to reduce the overall carbon footprint of the automotive industry. This means if your car didn’t pass, it’s using more fuel than it is supposed to be. When your car uses more fuel, it’s not only bad for the environment; it’s also bad for your wallet. So completing the necessary service and repairs to your vehicle might actually save you money in the long run. Of course, the best advice is to get regular inspections and complete the regularly scheduled maintenance

So your car failed a smog check. Now what? Luckily, when your car fails a smog test, it will come with a report on why it failed the smog test. This will usually give enough of a clue to a skilled technician as to what’s wrong with it, making it easier for him to fix it. So if you’re wondering how to get your car to pass smog, it depends on what is wrong with it. 

In some states, like California, the repairs to your car must be done by a designated smog check technician. If it failed the first time, then the repairs are completed, you must take it to a STAR facility. This is a smog check station that is designated by the state, not just a privately-owned auto mechanic shop. So if you’re wondering how to pass a smog test after it failed the first time, the simple answer is to get the necessary repairs, then have it tested again.

Can You Sell a Car That Won’t Pass Smog?

If your car failed its smog test, and you don’t want to splash out on the repairs, your next question might be, “Can you sell a car that won’t pass the smog test?” The answer depends on what state the car is registered in. In California, it’s illegal to sell a car that hasn’t passed a smog test within 90 days before the sell date. 

In other states, even if they require a smog test to get a valid registration, you can sell it without a passed smog test — but you may need written permission from your department of motor vehicles. When you make a car sale without a valid smog test, you will need to have both parties sign an agreement informing the buyer that the car is sold “as is,” and there are no guarantees that it will pass a smog test.

So you do have options for selling a car that won't pass smog, but it may be a complicated process — and it’s only legal in certain states. If you have a car whose engine won’t pass a smog test, and you’re unable to sell it due to legal reasons or because you can’t find a buyer who will buy it without a valid smog test, you have one last option, because it IS legal to sell your car for scrap

JunkCarsUS is the leading junk car buyer to answer your question, “What if my car doesn't pass smog test?” We can give you a top dollar instant offer for your car no matter how unsalvageable or totaled the condition it’s in, no matter the state you’re in, no matter the title it has, or if it has a failed smog check. We offer free towing, a highest price guarantee, and we even do all the paperwork for you! Our three-step process is the easiest and most hassle-free way of getting rid of your junk car. So if you’re all out of options on what to do with your failed smog junk car, give JunkCarsUS a call at (855) 547-1550 and see how much cash you can get today. 

Edgar Moulton.


Edgar Moulton. Car Expert

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