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How To Pass The Smog Test Legally?

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In many states, the emission test, better known as the smog test, is mandatory if you intend to drive the car legally on the road. It helps to calculate the number of harmful gases released in the environment through the regular operation of the vehicles.

We know that no vehicle can completely clear the smog test, but it can reduce to a certain extend. All this would help to reduce pollution and save our environment.

Thus, we at this moment provide you with the article that will help you to learn the ways which will tell you how to pass the smog test legally in your car. So, let’s begin.

What Is Smog In Vehicles?

The smog is produced when sunlight reacts with the nitrogen oxides and the other volatile organic compounds in the atmosphere. The car also emits nitrogen oxide, which results in smog, thus causing pollution.

Smog is harmful to our bodies as well as the environment. When we breathe the air containing pollution, it irritates our airways and increases our risk of severe heart and lung diseases. Because of these health risks, cities are having smog tests for vehicles.

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Several cities conduct smog tests to investigate the engine emissions of a vehicle or car. They identify and check vehicles that generate high levels of emissions. Those found to have such smoke-related problems fail the exam. Thus, we need to have well-maintained and eco-friendly cars.

How To Pass The Smog Test Legally?

Taking your car for a smog test is quite nerve-wracking and nervous too. As we all know, if our vehicle fails the test, we need to pay costly repairs, late DMV registration fees, and all other expenses that come with difficulty maintaining our vehicle.

All this could be very stressful. Thus we need to pass the test correctly to avoid these unexpected expenses and tension. So, here are few steps that will guide you to pass your smog test legally.

1. Check The “Check Engine” Light

A lit “check engine” is light is generally one of the main reasons for smog test failure in cars. If your “check engine” light is switch on, then it is an automatic test failure. That’s why you should get the light out before you go for a smog test of your vehicle.

The reason behind one of the check engine lights is a faulty oxygen sensor. This part ensures you about the correct gas-air balance; thus, its fault will result in more emissions, which is unsuitable for the environment.

So, it is better to visit a mechanic once before the test. If the mechanic asks you for any repair or replacement, get it done before the smog test otherwise, the check engine light will turn back on.

2. Go For An Oil Change

Dirty oil causes the emission of excessive carbon monoxide and other deadly pollutants, which are very dangerous for our health. These pollutants all together affect the greenhouse gases present in the atmosphere, thus causing air pollution. And with all these excessively pollutants gases, you will fail the smog test; hence this needs to treat.

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The dirty oil is rich in hydrocarbons pollutants which would increase the chances of smog test failure. So, try to have a fresh oil filled in your car before the test.

3. Take Your Car In For Its Routine Tune-Up

Before bringing your car to the smog test center, have it gone through the full tune-up service first. A new tune-up ensures your engine is running in total fine and good quality condition.

The mechanic could check and perform the necessary maintenance needed by your vehicle on the ride in the tune-up. All this includes various changes like topping up your coolant and gas tanks and changing the dirty filters of your car.

While performing the tune-up, you must keep in mind that this needs to perform at least a month before the test. During a tune-up, most mechanics disconnect the battery, which resets the computer. So, you need a minimum of 150 miles driving before the test.

4. Make Sure You Have Properly Inflated Tires

It would be better to confirm that your vehicle does not feel any drag while driving. The under-inflated tires are responsible for the creation of a certain level of drag within the car. The “drag” in return places more pressure on the transmission engine. This increased pressure insists the engine work more than required which results in more emissions.

The instability because of the under-inflated tires while going through the dynamometer also causes excessive emission. All these reasons will undoubtedly fail the smog test.

5. Get A Pre-Inspection Of The Vehicle

We usually are very nervous before the vehicle’s test, so the best way is to have a pre-inspection of the car before the test. The pre-inspection will reduce your tension and nervousness and also helps you to know about the vehicle’s chances to pass the test.

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Also, it is better if you, please get pre-inspection long before the test, then you would have plenty of time to fix all the necessary repairs before the actual test.

6. Drive Fast Two Weeks Before The Test

The catalytic converter is a vehicle that converts the less toxic gases and pollutants from an internally present combustion engine into less harmful substances before releasing them into the atmosphere.

But the catalytic converter works if the engine is hot enough to meet the requirement of the converter. For this, we need to drive the car at high speed over the freeway frequently within two to three weeks before the smog test to burn out any oil and gas residues.

What Prevents The Car From Passing Smog Test?

There are multiple reasons why often cars fail to pass the smog test, however the most common of them are listed below.

The very first cause is that you are past due for an oil change, you may have rich air to fuel ratio in your car, your vehicle may have worn a spark plug or leaking gas cap, and also there is a chance that your car has a dirty air filter.

How To Pass The Smog Test Illegally?

We do not recommend you do any illegal tricks to pass the smog test, so only try the mentioned ways above.


We hope all the readers have no more doubts and queries related to the topic. We also wish that you know how to pass the smog test legally and understand how important the test is for your health and your vehicle.

If your questions persist regarding the topic, comment below in the comment section. And we’ll surely answer all your questions as soon as possible.