Need to replace O2 sensor

My Engine light is on. I think it might need an O2 sensor replaced.
Experienced mechanics share their insights in answering this question :
When a Check Engine Light is illuminated it can be scanned by a tool. The code that gets read by the computer signifies what needs to be changed/replaced. An O2 sensor code quite possibly may be the case, but a mechanic can be certain by proper diagnosis of the Check Engine Light codes. After diagnosis, they will be able to pinpoint exactly what needs to be repaired.

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It is best to replace O2 sensors in pairs. For example, if you replace the downstream left sensor, you should also replace the downstream right. However, on most vehicles produced since 1996, replacing one sensor (especially the front engine monitoring sensor) will cause the ECU to set a code for the other sensors.
Oxygen sensors are not among the maintenance items that need to be replaced regularly, such as oil and air filters, so they typically are replaced only when they fail.
Generally, oxygen (O2) sensors last about 30,000-to-50,000 miles if you have an older car. Newer sensors can go 100,000 miles before they need to be replaced.
Traditionally, there are a couple of O2 sensors on your Silverado – Upstream and Downstream. They are located in different places but have the same functionality. You can find the Upstream O2 sensor on the exhaust manifold, while the downstream one is hidden under the catalytic converter system.
The oxygen or lambda sensor is one of the most important and one of the most misunderstood components of a modern fuel injection system.
Your car has at least two sensors, and when one of them goes bad, you need to do something about it. Can you clean an oxygen sensor? No, despite what you might have heard or read, such sensors should be replaced when they become faulty.
What Is The Life Expectancy Of An Oxygen Sensor? The life expectancy of an oxygen sensor is typically 30,000 to 50,000 miles. Even under normal operating conditions, oxygen sensors must endure a constant barrage of harm- ful exhaust gases, extreme heat and high velocity particulates.
A bad oxygen sensor could cause sluggish and rough driving with stalls, along with poor fuel efficiency and high pollution. And if you leave it there for several months, it may lead to serious problems in the engine and catalytic converter which cost thousands of dollars to fix or replace.
If you`re ever riding on the highway and smell something harsh from your car, that could be a quick sign that your O2 sensor is failing. If you ever begin to pick up on some changes like bad powertrain performance, engine misfires, or loud noises, that could be a symptom of your O2 sensor probably having issues.
There are two types of O2 sensors on your vehicle: upstream and downstream sensors. They essentially serve the same purpose, but are located in the different parts of your Silverado. The downstream oxygen sensor is located behind your catalytic converter.
Trouble Code: P0138 Oxygen Sensor Circuit High Voltage

Threaded into your vehicle`s exhaust pipes or exhaust manifold is a heated oxygen sensor (HO2S), which monitors your exhaust to see if the engine is running on too much fuel and not enough air or vice versa.

Bank One is always the bank where cylinder number one is located. On the Corvette it will always be the driver side. Bank Two is the passenger side. Sensor 1 on Corvettes is always the sensor that is closest to the exhaust port of the engine.
Poor Engine Performance

Will a bad O2 sensor cause rough idle and loss of engine power? You bet. Moreover, you may also notice poor acceleration, engine misfires, and even stalling. Bad oxygen sensors disrupt all kinds of essential engine functions, including engine timing, combustion intervals, and air-fuel ratio.

Why do O2 sensors fail? Since the oxygen sensor is in the exhaust stream, it can become contaminated. Common sources of contamination include an excessively rich fuel mixture condition or oil blow-by in an older engine and engine coolant being burnt in the combustion chamber as a result of an engine gasket leak.
Poor Fuel Economy

The oxygen sensor can affect how much fuel your vehicle`s engine burns. By measuring oxygen levels in the exhaust, the O2 sensor helps to ensure your automobile meters and delivers the correct amount of fuel depending on the demands you place on the engine.

A: Pretty much all of the O2 sensors are 22 mm (7/8″). From the description next to the picture: “Common 6 point, 7/8 in. (22mm) socket fits most oxygen sensors”.
Each oxygen sensor has its own unique characteristics specific to its application. One generic oxygen sensor that may appear to be the same cannot be used to replace a range of these specific oxygen sensors.
Typically, you cannot repair a faulty O2 sensor. It must be replaced because of the technology and materials in its housing. There are some DIY places that will tell you how to clean the sensor to get a few more miles out of it, but you`re only delaying the inevitable.
Your new O2 sensor should be handled like a piece of china. Do not allow the tip to touch anything—it may become contaminated. Apply a small amount of anti-seize to the threads and hand-tighten the sensor in the exhaust bung, being careful to keep the tip away from the sides.
Cycle the ignition OFF/ON 2 times with a 10 second pause in between key cycles. Check measured value block (MVB) 41/4 and 136/4 to verify they have both changed from a 1 to a 0. This forces the ECM to re-learn the O2 sensor adaptation.
The short answer is that our strongest gasoline fuel additive, B-12 Chemtool Total Fuel System Clean-Up (part #2616), and a good tune-up might indirectly solve your problems.
What effect do fuel additives and injector cleaners have on oxygen sensors? Fuel additives and injector cleaners that are labeled as “oxygen sensor safe” may be used in sensor-equipped vehicles. Use of additives not labeled as “oxygen sensor safe” can damage your oxygen sensor.
The catalytic converter, or cat for short, is responsible for removing harmful emissions from the exhaust. If the two O2 sensors collectively sense that the oxygen levels don`t change significantly after running through the cat, it`s a sign of a bad catalytic converter.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

check engine light O2 sensor already replaced same codes still popping up after replacing old O2 sensor
ANSWER : Hi there. What you received from the parts store was a code retrieval, not a diagnostic. The codes are set when a fault is detected against normal operating parameter. The computer does not know what caused the fault, only that the fault meets the criteria for this code to set. There could be a problem in the wire harness, converter, or the ECM. The code and data are needed to properly assess the direction that a diagnosis needs. I strongly suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a check engine light inspection.

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i need to replace both o2 sensors for vehicle listed above. so is it front left and back left o2 sensors?
ANSWER : Hi there:

Typically when an issue comes up with O2 sensors, it’s either the front bank (before the catalytic converter) or the rear bank (after). It’s very rare that all need to be replaced. However, the quickest and most effective way to determine which is faulty and need to be replaced is to have one of our professional mechanics complete a check engine light is on inspection. This service will allow them to determine which one is bad, and if you’d like, we can replace that O2 sensor for you.

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Check Engine light comes on, mechanic replaced o2 sensor but light still comes on.
ANSWER : Hi there:

If the mechanic completed the O2 sensor replacement, reset the codes and the error code was triggered again, it is possible that the catalytic converter is damaged and needs to be replaced. However, it’s also very common for the electrical harnesses that power these sensors to become frayed, damaged or faulty; which can also trigger the check engine light. It’s not advisable to drive a vehicle with a damaged catalytic converter for extended periods of time, as it can cause damage to internal engine components.

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Diagnostic code read o2 sensor bad, replaced o2 sensor, cleared code but engine light came back on, is it caused by bad air filter
ANSWER : Hello there. Typically jump starting a vehicle doesn’t trigger an OBD-II error code. However, one of the most common misdiagnosis issues with the P-2270 is replacing the O2 sensor before diagnosing if there are any exhaust leaks. Obviously, you’ll want to check for the exhaust leaks first, repair the damaged component, and then clear the codes before scanning the vehicle again. Sometimes the electrical harness attached to the O2 sensor is damaged or dirty which will also trigger this error code. The noise and vibration may be an indicator of a loose exhaust pipe, which may be the source of the error code staying on. If you need any help, have a technician from YourMechanic come to your home or office to diagnose your Check Engine Light and make the necessary repairs.

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I have a p0171 code on my ford ranger 2.5 and have replaced fuel filter maf sensor, iac sensor, fixed vacuum leaks, replaced fuel
ANSWER : Hello there. You might to read this article about the P0171 OBD-II trouble code; as it will give you ideas on causes and possible solutions.

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Need to replace Accelerator Pedal Position Sensor
ANSWER : The TPS and a scanner to test it is all that you need. The code P0122 points to the sensor but a through pinpoint test should be done to make sure the sensor is failing before you replace it.

If you need help with this, contact a certified mechanic who can diagnose your Check Engine Light code and make the necessary repairs to your vehicle.

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if the o2 sensor needs to be replaced. should you replace them all if none have ever been replaced at 114000 miles
ANSWER : Normally, if there is a question as to whether the sensors need to be replaced, checking the datastream with a diagnostic scanner will show how well the oxygen sensor is performing. A couple of things to note about oxygen sensors is that they are responsible for monitoring the oxygen levels in the exhaust so that the control module can adjust the amount of fuel, and therefore, will have a direct effect on mileage and performance. Also, most vehicle manufacturers will list an interval for changing the oxygen sensors, and is normally listed in the owners manual. If you feel you could use some help with diagnosing and/or repairing an issue, contact a certified mechanic, like the mobile mechanics at

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So I had two codes come up for two of my o2 sensors..replaced them both and check engine light is still on…my mechanic seems to
ANSWER : Hi there:

Although it’s hard to say if there was serious damage done to your ECM during this service, it’s more likely that the stored error codes were never cleared from the ECM, and that’s why the warning lights still appear. This is a common oversight with some mechanics, but if you have a mobile mechanic complete a check engine light inspection, they should be able to clear those stored codes and determine if further damage has occurred.

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