Why did my check engine light come back on after replacing O2 sensor?

Fiance’s dad cleaned out the mass air flow sensor and ran the car a bit more with the old O2 sensors on and the car was running great again, but check engine light came back on with same old codes. I returned the O2 sensor that had the high resistance reading than spec and got a new one, replaced them.

How does the O2 sensor in a car work?

The O2 sensor in your vehicle monitors the exhaust gases coming out of the engine. It determines the amount of oxygen in the gases, which indicates how well the fuel is being burned. The O2 sensor then sends information to the electronic control unit, or ECU, the vehicle’s computer.

When to reset the ECU after changing an O2 sensor?

Sometimes an O2 sensor fails, and you need to replace it. Once you’ve replaced your vehicle’s O2 sensor, you’ll need to reset the ECU so it can properly gather information from the new O2 sensor.

How long does it take O2 sensors to show Ready?

Drive the car almost 300 miles in various conditions and still won’t show ready. This really sucks. I struggled with this as well when trying to pass smog with a tune. i was finally able to get them to reset by driving real hard. Need to get the exhaust temps. high to get the 02 heat to reset. That’s one of the two things failing.

How can I tell if I need to replace the oxygen sensor?

If it is not within spec replace the sensor. And as stated earlier depends on your emissions rating, pins number three or number number will be the power supply. With the key on engine off you should see battery voltage to one of those pins.

When do you need an O2 sensor in your car?

Both to improve engine efficiency and minimize emissions, vehicles manufactured after 1980 have at least one O2 sensor. With few exceptions, automotive internal-combustion engines require a oxygen-to-gasoline ratio of 14.7:1.

Can a bad O2 sensor cause an illuminated check engine light?

Faulty O2 sensors are a common cause of illuminated Check Engine Lights. Still, because the light may indicate a variety of other problems, it is important to watch for bad O2 sensor symptoms. If you notice any, repairing the problem as quickly as possible is a good idea to prevent further trouble.

What should I do if my check engine light comes on?

My check engine light came on, changed O2 sensor. Check e… Q: My check engine light came on, changed O2 sensor. Check engine light was still on, then three days later went off. My check engine light came on and was solid, not blinking, my mechanic reset my sensors, but it didn’t help.

What should I do if my oxygen sensor is not working?

Check the voltmeter. It should read close to 800 mV in response to the reduced oxygen entering the engine. If it doesn’t, there’s likely something wrong with the O2 sensor. After replacing your oxygen sensor, try to visually inspect the old sensor to see if you can identify the problem.

Which is the most troublesome check engine light code?

O2 sensor codes are often the most troublesome and misdiagnosed check engine light problems. It is my hope that this short oxygen sensor article will open your mind on the subject. There are other possibilities besides bad sensors that will set these kinds of trouble codes.

What is a bad O2 sensor?

Bad O2 sensors are one of those car problems that most drivers tend to postpone until more serious problems occur. These symptoms will rarely cause any immediate damage, but over time, if left unattended, they can cause damage to the engine and other systems mainly through improper air-fuel mixture.

What is an O2 sensor?

An O2 sensor is an electronic sensor designed to measure the oxygen level in the exhaust fumes that exit the engine after combustion. All combustion engines burn fuel by mixing it with oxygen, which is essential to run the engine.

What are the symptoms of a faulty oxygen sensor?

The most common symptom related to a faulty oxygen sensor is a sudden (significant and almost immediately noticeable) drop in your vehicles fuel economy. Other immediately apparent effects of a defective sensor is a drastic change in engine performance, overall power, and response.

Where is the O2 sensor on a car?

On almost every car, there is an O2 sensor located in the front, on the exhaust pipe, or manifold, and there is an O2 sensor located after the Catalytic converter. The front O2 sensor is the most important because it monitors the air/fuel ratio.

Do you need to replace your oxygen sensor?

Replacement of good oxygen sensors is one of the common mistakes that both seasoned auto repair mechanics and do it yourself driveway mechanics will make when tackling rich or lean diagnostic codes. I am not saying that these O2 sensor codes never require the replacement of the sensor itself.

How does one check the O2 sensors?

Testing (O2) Oxygen Sensor Voltage Signals Start the engine and check the sensor voltage signals on your voltmeter . The sensor voltage should cycle or fluctuate within the 100 mV-900 mV (0.10 to 0.90V) range. Hence, This means the sensor is operating properly.

When to replace O2 sensor?

Car manufacturers recommend replacing the O 2 sensor about every five years (one- and two-wire sensors) or 10 years (three- and four-wire sensors). However, silicon or carbon soot may cover an oxygen sensor due to a car repair or engine performance problems.

Where is the oxygen sensor located on the engine?

Oxygen sensors O2 sensors will always be located in the exhaust system. Their function is to sense how much oxygen remains in the exhaust that is flowing out of the engine, and report that information to the vehicle’s engine control computer.