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Oxygen sensor

My 2001 Nissan Sentra’s engine light came on recently and my mechanic detected (from the code) a bad oxygen sensor or cat. I have ALWAYS used a certain brand of gasoline in my car since it was born, and I switched to cheaper. My mechanic canceled the code, and since I started using my brand name gas, it has not come back on. Would switching gasoline have triggered some kind of emission failure?

Curious, and so is my mechanic (although he says no).

no code=no help.

It is possible, although it is more likely that the code will eventually come back on. If not, then it is possible you got a bad batch of gasoline.

The trouble code NEVER says that a sensor (or, other part) is faulty. The trouble code alerts you to the circuit the sensor is a part of.
Why the code came up? Who knows? Sometimes flukes happen. That code may never come back.
That mechanic will cost you in the replacement of parts with no defects. Change NO parts just because a trouble code came up.

EXACTLY,codes will remain in HISTORY menu,and codes are a GREAT START,to further DIAG veh,and lead u to proper steps to do so.

A bad batch of gas is a possibility depending on where you went. It also could be the sensor got dirty or wiring came loose. Basically, anything that could prevent the sensor signal from being read by the computers would cause the fault code. So who knows? The mechanic fiddling around could have inadvertently addressed a loose wire or bad connection.

There is very very little difference from one brand of gas to another. Often one supplier supplies several different brands. However you can get a bad tank full from any brand.

That said, I would not bet that was it. If you still have a problem the light will come back (assuming the mechanic did not use the black tape method of canceling the code.

Get the real code (like P0123) not an interpretation of what it means. Some auto parts stores will give it to you for free.

Well, the light did come back on. My other question is: My mechanic uses a hand-held device to check the “engine light code” and not a very expensive computer diagnostic machine that many shops now have. Is there a difference? Could he be reading a wrong code?

nope same info.

next time get the actual code. it is the format of P 0123

report the code back here. NOT the code readers interpretation of it. no short hand. just the code.

huge difference in the equip,code readers for codes only,good scan tools we can look at all paramiters,within that sub system,and see what the puter sees,not in real time ,but we have a graph function for that when narrowed down . so HUGE diff.

The code was P 0420 the same code that comes on everytime. I think he said the front bank.

My mechanic has now installed a small computer device to my car which will monitor everything as I drive it over the weekend. Then he will put it on his computer to see exactly what is happening with my car. Have you all ever heard of that gizmo?

well, now my mechanic has plugged in a small electronic device that will monitor everything that is going on with the codes. I am to drive it around a few days and then he will hook up this device to the computer and see what is going on. Have you all ever heard of such a gizmo?