Check Engine light comes on, mechanic replaced o2 sensor but light still comes on.
Check engine light comes on, mechanic ran diagnostic and said it needs o2 sensor replaced. He replaced it but light still comes on. Mechanic ran diagnostic again and said it still is showing bad o2 sensor but since he replaced it the problem must be a catalytic converter that is plugging up and should be replaced. Since replacing a converter is costly I want to make sure this is the problem. My question; could this be something else or does the converter need to be replaced? Second question, is it okay to run the vehicle if the converter is the problem?
My car has 122000 miles.
My car has
Experienced mechanics share their insights in answering this question :
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.
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.
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.
Usually a reset is performed after 2–3 drive cycles after the problem has been repaired. I have had drive cycles complete after about a 3 miles test drive and then on other vehicles, it took 20 miles.
The reasons for a check engine light turning on can range from something minor like a loose gas cap to something more serious like a faulty catalytic converter. It could even be a sign of internal engine failure. Ignoring the problem can turn a potentially quick fix into a costly and time-consuming repair.
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.
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.
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.
It is a good idea to let your car sit with the battery disconnected for at least half an hour, this will reset the computer allowing your O2 sensors to not have to work against the PCM.
Newer oxygen sensors are supposed to work efficiently for 60,000 to 90,000 miles, depending on the model of your car. If your mechanic determines that your car`s problem is due to a bad or failing oxygen sensor, the replacement shouldn`t take long and you`ll be ready to tackle many more miles on the road.
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.
Will your check engine light turn off by itself? 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”.
Check your gas cap first. Many vehicles have a loose gas cap indicator that will be triggered before your check engine light comes on. If your gas cap is loose or the seal is not tight, the vapor leakage can cause your fuel system to trigger the check engine light.
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.
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.
If the problem was a bad sensor, it will work immediately. It might take a couple of drive cycles to auto clear the codes from the ECU. If another issue caused the code, like a bad wire harness, then the light will never go off until that gets fixed. Same thing for a bad cat convertor.
No reset is required. Most of the time, there`s a problem when the check engine light is on.
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.
If the problem was a bad sensor, it will work immediately. It might take a couple of drive cycles to auto clear the codes from the ECU. If another issue caused the code, like a bad wire harness, then the light will never go off until that gets fixed. Same thing for a bad cat convertor.
It is a good idea to let your car sit with the battery disconnected for at least half an hour, this will reset the computer allowing your O2 sensors to not have to work against the PCM.
However, if there`s a problem, the light will come back on as soon as the computer runs the test that caused the light in the first place. It might happen right after you turn the car on, which might make it seem like you can`t clear the check engine light. Or it might take a couple of days to come back.
It is a good idea to let your car sit with the battery disconnected for at least half an hour, this will reset the computer allowing your O2 sensors to not have to work against the PCM.
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.
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.
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.
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.
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.
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.
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.
2006 Ford Mustang has check engine light on
ANSWER : There are countless potential causes for your illuminated check engine light. The mechanic manually turned off the light, but it came back on because the problem has not been fixed. The first place to start is retrieval of the stored diagnostic trouble codes (DTCs). These codes serve as a starting point for any further diagnostics a mechanic may perform. Codes will be stored anytime the check engine light is on. Since the first mechanic was unable to fix your concern, I recommend giving the professionals at YourMechanic a call. We offer expert check engine light diagnosis and repair.
p0011 code,check engine light one, changed bank 1 vvt solenoid and check engine light still on?
ANSWER : The P0011 code is typically caused by oil issues with the car. I would particularly make sure the engine oil level is not low. The VVT solenoid relies on proper oil levels to do their job. If they don’t have enough oil, they won’t work. You can have a mobile technician from YourMechanic visit your home or office to inspect the Check Engine Light for you. If you follow through with a repair with us you will be reimbursed for the cost of inspection.
