Error Code..at a loss

I have a 2001 TRD pre-runner extra cab 2x4 3.4 V6 w/ error code p0171 (lean fuel) 116,000 miles

I changed o2 sensor, came back on
Cleaned MAF - came back on
Replaced MAF, came on after 60 miles
Replaced Fuel Filter - came back on
I can find no leaks in the intake -

any help would be nice or should I just bite the bit it and take it to the dealer?

 

what fuel pressures are you running at?

 

This might sound stupid or far fetched but have you checked your air intake im not familiar with how different vehicles are from a motorcycle carb( I know your truck doesn't have a carb) just trying to compare the systems. But have you checked your air filter? Have you tried running the truck with air filter pulled out and air box open see if it will suck more air in to even out the air to fuel ratio in the truck? Again this could be completely wrong but maybe worth a shot?

 

I'm not sure or even know how to check that.

 

I have the standard air filter, ya know the White one, no K&N

 

Have you tried multiple different code readers it could be something really stupid just to make to code pop up and when you researched it and spent all this money on trying to fix it it's something so dumb and pointless you missed it try a different reader see if it pops up same code

 

download thr FSM in the sticky thread and follow you testing procedures and instructions there

 

Just pull it out leave your air box open reset the code and see if it still pops up that way too like I said I could be completely wrong but worth trying it out

 

I just took it to auto zone (two different ones) to get the code. then went to a mechanic and they pulled the same code.

The filter is new. I will try it, cant hurt. But can it hurt not having filter in the long term?

However, I went from east coast (mid atlantic) weather to the southwest. can climate make that much of an impact on lean fuel?

 

try pulling the EFI relay in the fuse box under the hood, leave it out for 15 minutes to reset the ECM and see what happens.

I think you should change the front o2 sensor, it wont hurt and probably needs changing anyways and that may be all that's wrong because it tells the engine what the fuel/air mix is to be set at

 

I did, it's brand new, not even a month old. I listed that in the first post. It's the second one. I had this problem a few years ago. Then, changing that fixed the code, not this time.

 

then you might have a wiring issue, download the FSM and start following the test procedures in it.

 

Changing climates shouldn't do that much to your engine that's why I'm pointing at the fact that it's something stupid I just meant take out the filter and reset the code see if it comes back on if not then it has something to do with your filter not giving the engine enough air causing lean fuel if taking the filter out works I'd suggest Chang to a CAI set up to get more air into your motor but weird circumstances

 

And maybe even just disconnect the battery till it resets everything plug it back in maybe the new sensor hasn't been calibrated with the engine and is freaking it out?

 

Man, I've done all of it, multiple times. lol...

 

did you use oem denso parts? aftermarket electrical parts cause all sorts of problems on these trucks, always use oem Toyota or denso or asin parts only.

I have seen aftermarket brand sensors cause issues and throw codes because they just don't communicate well with the electrical system

 

yes I did..

 

Maybe try a fuel system cleaner like Lucas or something; perhaps some injectors are stuck/sticking closed. Maybe the fuel pump relay is going nite nite. Keep in mind I am quite probably WAAAY wrong. Good luck.

 

Have you changed both o2 sensors? I see you said you changed one.