Q: My check engine light came on, changed O2 sensor. Check engine light was still on, then three days later went off.

asked by on July 29, 2017

My check engine light came on and was solid, not blinking, my mechanic reset my sensors, but it didn't help. Took my car to an exhaust place, they said it was my O2 sensor or my catalytic converter. I had them change my sensor, drove 10 miles and my check engine light came back on, so I figured it was the catalytic converter. Three days after that, the check engine light turned off. I called the exhaust place and they said it was ok to continue driving. How do I know for sure what is going on with my car?

My car has 148377 miles.
My car has an automatic transmission.

Hi There, The last diagnosis is correct in that the sensor replaced caused the check engine light to turn off. In some cases they do not always turn off immediately and take a bit of driving for the computer to recalibrate and recognize that the problem has been corrected. In your case, it sounds like the oxygen sensor is what caused the code to be triggered. This can also sometimes cause codes to be triggered that may reflect problems with the catalytic converter as well since the oxygen sensor reads the exhaust gases coming from the catalytic converter.

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