I have a 00 maxima with 200,000 miles. Got this code 2 years ago and they said its one of the the catalytic convertors. Replaced the catalytic convertor after driving with the service engine soon light for about a year. But it cost me about $900.
Things have been running fine for about a year but now the P0171 code is back. I'm having a rough start up when the engin is cold for about 30 seconds in the mornings only, then it runs great. I saw a leak around the PCV valve and changed it and its hose. I turned the light off and it didn't come back on for about a month. But now it's back again
I'm reading now that its the O2 sensor on one of the banks or the MAF sensor. Please help me and tell me its not the catalytic convertor. Any help would be greatly appriciated.
I'm coming up with a possible solution being to clean the MAF sensor and maybe replacing the O2 sensor on bank one. Does that sound it would solve my problem?

 

I would begin by testing the MAF. theya re very cheap on www-car-aprt.com, or new from DAVEB.

 

I kept getting P0171 and P0174 (and pinging on and off) for quite a while on my 2000 GLE. Finally replaced the MAF. No more pinging, no more P0171 and P0174 and car runs great (except now I'm getting P0400 EGR - a separate problem apparently, haven't gotten around to getting that fixed).