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Persistent P0140 Code - Buick 3.8

The P0140 code persists after I have replaced the O2 sensor and EGR valve on my 1996 Park Avenue (115K). The engine, however, runs flawlessly. Besides any suggestions to remedy this problem, is it advisable to take a road trip and ignore the problem?

Did you replace the O2 sensor after the catalytic converter?


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Hmm, I actually didn’t know there was one after the converter. I replaced the sensor just in back of the engine.

The code is for the O2 sensor after the converter.


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I just went by what the counter guy told me - - lesson learned. I see now that you have responded that there are “upstream” and “downstream” sensors. I’m going out now to try and locate it.

Sensor found and replaced. Code removed. We’ll see what tomorrow brings. Many thanks.


Success. Much appreciated!