DTC p0171 System too lean (bank 1)

[Ashvin]

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?

[DevonD]

you got alot of miles on that thing...Another car I had the MAF went wacky and it did similar things, but it ran really poorly all the time, not just start up.. So ya I would start out cleaning that.

When was the last time you did plugs? and what did you use? only NGK's will work in these cars. Check out those injectors too. But ya..MAF makes the most sense to me. I will think more about it tonight and if I come up with anything else I will let you know!
Modified by DevonD at 12:44 AM 6/18/2008

[MinisterofDOOM]

It could be an O2 sensor. Probably the one in the rear exhaust manifold if it's bank 1 specific.

I doubt it's a bad catalytic converter again. And if it was MAF-related, the car would most likely be running poorly.

If the car is running well, I'd say you're on the right track as far as replacing the bank 1 O2 sensor.

[Mike G]

I would start with the MAF cleaning and run a can of BG44k through the fuel system, then go from there....--Mike

[NutriaforBreakfast]

I would clean the Idle Air control valve too

[Ashvin]

I ordered the new O2 sensor and will install it this weekend and also clean the MAF sensor. Hopefully that will solve it. Do I have to reprogram the ecm?