How To Pass Emissions Test With Bad O2 Sensor


When your car is working properly, it can sometimes be difficult determining what functions are working and what are not. For example, when you start up the vehicle, it may take a few minutes for everything to run smoothly and at a full speed.

If you look closely, you will notice that while the engine is running, there is a lot of movement and vibration. This is because parts of the engine work together and need to constantly shift in order to function correctly.

When talking about cars, there are two major components that play an integral part in how well they operate: the engine and the transmission. The engine produces energy which powers the wheels via a series of hydraulic motors that connect directly to the axle shafts.

The transmission then takes this power and shifts it into different gears depending on what mode the driver selects. In sports mode or drag race modes, more gears mean faster speeds due to gravity helping pull the vehicle down.

In eco-drive or economy mode, fewer gears means lower top speeds and better fuel efficiency. However, less powerful engines require additional attention in terms of maintenance and performance tweaking.

This article will focus on one common cause of failed emissions tests – bad oxygen sensors! If you would like to learn more about other potential causes, check out our list here. We also have a section with helpful tips if you are experiencing some sensor issues.

Replace the oxygen sensor

how to pass emissions test with bad o2 sensor

The first thing you will need to do if your car is giving poor fuel economy is to have it checked out whether or not it is broken. If the vehicle does not run properly due to a bad sensors, then you can get a new one from most any automotive parts store.

Most cars now use computers to control all of their functions so replacing this part would be done digitally. Therefore, an expert mechanic would have to test the computer before they could install the new sensor.

But instead of paying a large amount of money for a brand new sensor, you can easily find used ones online or at some automobile dealerships. Some people even sell them from the sites that they purchase the vehicles off of!

Once you have found a good working sensor make sure to buy it along with the appropriate wires so that it works for your car.

Make sure the engine is not flooded

how to pass emissions test with bad o2 sensor

A poor performing oxygen sensor can cause your vehicle to be over-oxygenated. This may result in dangerous high levels of fuel being mixed with air, which could cause smoking, combustion instability or even fire!

To check if this is the case, use an accurate O2 meter to determine how much oxygen there is in the mixture. If it is very close to zero, then you have this issue.

If you feel that your car is running out of gas quickly, make sure this is not the case! You can try cleaning the exhaust tip, but only do so if you are certain it has come into contact with gases. Do not attempt to replace the sensor unless you have professional help

Your vehicle should also display a warning when the sensor fails. This will alert you that something is wrong and prevent you from driving away. Check all sources for such warnings though as some give more information than others.

Run the engine for a few minutes to check the oxygen sensor reading

how to pass emissions test with bad o2 sensor

If your car is giving very poor mileage with a bad or missing oxygen sensor, it is important to recognize what kind of vehicle you drive. Does this apply to yours? You might be able to tell by looking at your dashboard.

Most cars have two sensors that measure the amount of oxygen in the exhaust gas. One measures the amount of fuel burned, while the other checks to see if there’s an excess of air instead. A normal mix usually has enough oxygen to burn all the leftover gasoline.

If there’s too much air, though, the combustion doesn’t happen as well, which means less power. It also allows more unburned hydrocarbons to exit the tailpipe, increasing greenhouse gases. Both are harmful to our environment.

Confirm your test location is accurate

how to pass emissions test with bad o2 sensor

The second part of checking whether or not your car will pass an emissions test is confirming that your test site is reliable. Many people check their cars at local auto dealerships, but it is important to know that some of these facilities are more likely to fail than others.

It can be quite difficult to tell which ones are trustworthy because there is no standard set way to do emission tests. Some states require professional technicians to perform the tests, while other states allow anyone with basic skills to verify them for you.

Making sure the testing facility is reputable is very important as you could potentially lose money if they give you false results. It is also important to consider how expensive the test is before agreeing to pay for it.

Use the correct test kit

how to pass emissions test with bad o2 sensor

When your car is emitting excessive amounts of pollutants, it will purchase an aftermarket sensor that does not work correctly. These sensors are designed to determine if there are enough oxygen molecules in the mix coming off of you as combustion for fuel to meet the demands of the engine.

If this doesn’t happen quickly enough, then the engine won’t run because it thinks there’s not enough air to burn!

These wrong sensors can actually cause your vehicle to fail its emissions tests, which would cost you money in fines! Luckily, CarProof has a lot of tips on how to identify if this is happening to your vehicle, and what to do about it.

We have also compiled a list of cars with bad or missing O2 sensors so you know what vehicles to look out for when testing.

Let the engine warm up for a few minutes

how to pass emissions test with bad o2 sensor

Once you have made sure that your car is fully fueled, let it sit with the windows open for at least five minutes. If possible, do this in a parking lot or somewhere where there are many people around.

This will give enough time for the oxygen sensors to reach operating temperature. The sensor measures how much oxygen is present in the exhaust gas as it leaves the vehicle. When the sensor registers no drop of oxygen, then the bad sensor has failed and can be replaced!

If your car does not have an easy way to access the sensors, you can use a multimeter to check if the voltage drops when the sensor detects empty oxygen levels.

General Motors cars such as the Cruze and Volt typically have red wires connected to both sensors while Ford cars like the Focus have blue ones.

Slow down and keep your foot on the gas

Recent developments with poor performing oxygen sensors has prompted some automakers to install what is called an EGR or exhaust gas recirculation system. This sensor monitors whether there is enough oxygen in the exhaust, and if it does not see enough, it adjusts how much fuel is injected into the engine.

By reducing the amount of un-reacted gasses coming back out of the tail pipe, more oxygen can be used in the combustion process, thus improving performance. However, too much EGRS (exhaust gas re-circulation) can cause burning, which will hurt mileage and increase emissions!

Some cars have very sensitive EGR systems that are easily fooled by contaminants found in diesel engines. If you notice speedier acceleration than normal while cruising at highway speeds, chances are good that it is due to active EGR. Check under the hood for any kind of fluid going up in temperature, as this may indicate something wrong.

If possible, try driving around for a few minutes before taking off to ensure the car gets properly tuned. Once you do get going, stay within regulation limits and check your gauge frequently to make sure everything is working well.

Use the correct oxygen sensor reading calibration chart

how to pass emissions test with bad o2 sensor

Recent developments in technology have made it possible for cars to control when they are equipped with an adequate amount of oxygen sensors. However, not every car comes with good quality sensors that work properly!

If your vehicle receives the following error code: “OXYGEN_SENSOR_MALFUNCTION” you will need to replace the bad sensor ASAP as this can cause severe damage to your engine.

Fortunately, there is a way to identify which sensor is faulty by using an Oxygen Sensor Calibration Chart. Many auto repair facilities and websites offer such charts so that you do not need to go through hassle of buying one yourself.

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