I have a 2002 Grand Prix with a 3.1L engine. Recently the check engine light came on. I went to Auto Zone and they pulled the codes. It came up with a P0420 code. The guy at Auto Zone said that the problem was probably an O2 sensor.
The car smells of gas when sitting at idle but it doesn't run bad. I haven't noticed a lack of power but the gas milage has dropped quite a bit. Will a bad O2 sensor cause it to run very rich?
I read through all the posts (all 57 pages of them) but I couldn't find any with similar problems. Does anyone have any other idea's or should I replace the O2 sensor and go from there?
Any help would be appriciated.
