after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

Engine light on after repacing sparkplugs and wires which sensor do i change as suggested by diagnostic test give by autopart store?

My car has 120000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
Hello. If the scanner indicated the O2 sensor was bad, I would recommend replacing. The oxygen sensors are located in the exhaust system of the engine, and they sense the oxygen content of the exhaust gases. There should be two O2 sensors on this model engine, one on either side of the catalytic converter.

The sensor located just in front of the catalytic converter measures the mixture of the exhaust gas exiting the engine. The sensor located after the catalytic converter is used to measure the performance of the converter by comparing the O2 levels before and after. (Upstream is the same as pre-catalyst, before the catalytic converter. Downstream is post-catalyst or behind the catalytic converter). The amount of oxygen in the exhaust varies according to the air/fuel ratio of the fuel injection system. The oxygen sensor produces a small voltage signal that is interpreted by the electronic control unit (ECU) of the fuel injection system. The ECU makes constant adjustments in fuel delivery according to the signal generated by the oxygen sensor in order to maintain the optimum air/fuel ratio. If you would like to have this done, a certified technician from YourMechanic can come to your car’s location to replace the oxygen sensor if needed.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

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.
In most cases, successfully repairing the issue that caused your light to come on will cause the check engine light to turn off automatically—but only after 10 to 20 “cycles”.
Yes, a bad spark plug can confuse your car`s internal computer and trigger the O2 sensor code.
The Light Stays On

If you`re experiencing this, don`t panic. You may think that there is still a problem with the car after the repair, but it`s because the light needs time to reset. The car`s internal computer only resets after a set period where it checks all of its sensors once more.

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.
How do you reset your computer after replacing the O2 sensor? You don`t “reset” the computer. You just clear/erase the memory code and all is well in the world. If the repair was done properly the check engine light will stay off unless there is another concern.
You don`t “reset” the computer. You just clear/erase the memory code and all is well in the world. If the repair was done properly the check engine light will stay off unless there is another concern.
If the mass air flow sensor or oxygen sensors are not accurately reporting the air that`s coming into the engine or the oxygen content in the exhaust stream, it could cause a rich-running condition that can cause carbon to foul the spark plugs.
MALFUNCTIONING AND FAILED SENSORS Oxygen sensors can fail when the sensor`s ceramic element is exposed to certain types of silicone compounds or when an oil-burning engine leads to the sensor becoming oil-fouled. Also, a small amount of tetra-ethyl lead in the gasoline can kill an oxygen sensor.
Normally it won`t reset on its own. Once you`ve changed the sensor you should clear the error code using an OBDII tool. If the repair was successful the light won`t come back on.
Will the check engine light reset itself? The check engine light on your Mercedes-Benz will usually shut itself off if the issue or code that caused it to turn on is fixed. For example, if the cause of your check engine light coming on was a loose gas cap, if it`s tightened, the light will turn itself off.
To calibrate the sensor, follow the normal 2-point calibration procedure. -For the first point, push and hold the calibrate button on the sensor using a paper clip or LabQuest stylus. -Enter a value of 0 for this reading. -Release the button and take a second reading in air.
Can I Drive My Car With A Bad Oxygen Sensor? We recommend against driving with a bad O2 sensor as the powertrain is not running on the correct fuel mixture. While it may perform fine in the beginning, if your engine is running rich and using too much fuel it might begin to clog the catalytic converter.
Non-Continuous Monitors

The heater will bring the sensor up to operating temperature within 20 to 60 seconds depending on the sensor, and also keep the oxygen sensor hot even when the engine is idling for a long period of time.

A sputtering car may be a sign that your new O2 sensor is not working properly. The new sensor may be defective or could have been installed incorrectly. The issue could be tied to a myriad of other reasons within the fuel system, however. There may be an issue with the fuel pump, the fuel filter, or the fuel injector.
The accuracy of the sensor is the maximum difference that will exist between the actual value (which must be measured by a primary or good secondary standard) and the indicated value at the output of the sensor. Again, the accuracy can be expressed either as a percentage of full scale or in absolute terms.
Disconnecting your battery and draining the power to cause an ECU reset is one of the most common fixes for a check engine light that won`t go away on its own. Doing so is equivalent to a hard reboot on a desktop computer, which is a standard way to eliminate many common problems.
As we said in the title of this blog post, a bad O2 sensor can affect your engine`s performance. If the oxygen sensor sends readings to the engine control module and it incorrectly increases the air in the combustion chamber, you will experience spurts of power loss when you accelerate and drive.
To make sure the check engine light does not reappear, it`s recommended that you drive your car 30 to 100 miles. This enables the vehicle`s “Drive Cycle” to reset, as the various sensors need time to recalibrate.
Since most BMW models use a Condition-Based Servicing system, your check engine light should reset itself automatically if and when the offending issue has been resolved.
Yes. While the damage may seem small initially, the longer you drive with a bad oxygen sensor, the worse the damage will become. Eventually, you may experience rough idling, poor acceleration, engine misfires, an illuminated check engine light, and failed emission tests.
The ECU is a control system that uses feedback from the sensor to adjust the fuel/air mixture. As in all control systems, the time constant of the sensor is important; the ability of the ECU to control the fuel–air ratio depends upon the response time of the sensor.
Oil leaks are an often-overlooked cause for sensor failure. A vehicle with external oil leaks can result in multiple oxygen sensor replacements. For example, if a vehicle has a leaky valve cover gasket, oil may be leaking down the outside exhaust and into the oxygen sensor`s air ports.
The most common causes of misfires are worn, improperly installed, and mishandled spark plugs, malfunctioning ignition coils, carbon tracking, faulty spark plug wires and vacuum leaks.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

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.

Read Full Q/A … : after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

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.

Read Full Q/A … : after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

Engine will not stay started. I have replaced idle control valve map sensor spark plugs spark plug wires no check engine light is
ANSWER : You have a problem with the distributor assembly. I recommend replacing the distributor assembly. This will replace all the possible sensors and coil for the ignition and fix the problem you have.

Read Full Q/A … : after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which
ANSWER : Hello. If the scanner indicated the O2 sensor was bad, I would recommend replacing. The oxygen sensors are located in the exhaust system of the engine, and they sense the oxygen content of the exhaust gases. There should be two O2 sensors on this model engine, one on either side of the catalytic converter.

The sensor located just in front of the catalytic converter measures the mixture of the exhaust gas exiting the engine. The sensor located after the catalytic converter is used to measure the performance of the converter by comparing the O2 levels before and after. (Upstream is the same as pre-catalyst, before the catalytic converter. Downstream is post-catalyst or behind the catalytic converter). The amount of oxygen in the exhaust varies according to the air/fuel ratio of the fuel injection system. The oxygen sensor produces a small voltage signal that is interpreted by the electronic control unit (ECU) of the fuel injection system. The ECU makes constant adjustments in fuel delivery according to the signal generated by the oxygen sensor in order to maintain the optimum air/fuel ratio. If you would like to have this done, a certified technician from YourMechanic can come to your car’s location to replace the oxygen sensor if needed.

Read Full Q/A … : after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

O2 sensors changed, but check engine light still showing code after clearing it I checked fuse. Wires are good and used Denso OE.
ANSWER : Depending on what the code was for will determine if the oxygen sensor was to be replaced. If the conditions were for a rich or lean mixture and it said oxygen sensor, then the spark plugs and wires could need replaced if its a rich reading or the fuel injectors could be clogged or not working if its a lean mixture. If the code said that the oxygen sensor was bad, then check the harness and see if there is a break in the wiring or a short to ground in the wiring from the oxygen sensor to the main harness. If you need further assistance with your check engine light being on, then seek out a professional, such as one from Your Mechanic, to help you.

Read Full Q/A … : after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

I have a 96 Ford ranger with cel p0340 I have recently done a timing belt, engine runs great replaced cmp sensor cel still on
ANSWER : Hi There,
This may happen for a couple of reasons. First, check to be sure that the connections to the sensor are clean and not faulty or broken. Secondly, check to be sure you replaced the correct sensor as there are two camshaft position sensors in some applications. If you need further help with this, please reach out to us here at YourMechanic as we are always here to help.

Read Full Q/A … : after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

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.

Read Full Q/A … : after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

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.

Read Full Q/A … : after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

Eric smoalih

I am a certified master technician with the National Institute for Automotive Service Excellence (ASE), and I have been working as an auto mechanic for over 15 years. I am passionate about my work, and I take great pride in helping people keep their cars running smoothly.