I have an 01 Nissan Sentra. My service engine light came on and a mechanic told me that it was my catalytic converter. I replaced the converter but that wasn't the problem. The light stayed on and I brought the car to a different mechanic and they told me that it was 2 of my oxygen sensors. The scanner was reading the codes p430 and p420. I replaced both of the oxygen sensors and we reset the system and the light came back on. Can anyone give me any information on what's going on?

I would find a nissan mechanic.. every different mechanic you go to is going to tell you something else is wrong and charge you an arm and a leg. Or you can take it to AAMCO and they will give you a free diagnostic and tell you why the light is on. My old car (06 aveo) I took it to pep boys and they told me I had $600 worth of work on my car (I didn't even own it a year) and I took it to the dealership, and they ran a diagnostic, and said nothing was wrong with my car, they went over everything the shop did, and it was all fine. So they saved me $600 be careful out there.

Also, its common that's sometimes the circuit could be bad and keeping the light on. A pinched wire maybe?