p0171 Code

I have a 2003 v6 Tacoma with 265000 miles and I have been trying to resolve a p0171 code for over a year. A lean condition in bank one is detected, and the fuel trim level go wild ( short term go to around 20 and long term go to around 31 ). This condition is intermitted. I noticed the code is thrown after the motor is warmed up and is typically above idle (according to the saved data when the p0171 code is thrown). In the past year, I have replaced the fuel filter, MAF sensor, up and down stream O2 sensors, solenoid purge valve, pcv valve, and catalytic converters.

After I replaced the catalytic converters and the up and down stream o2 sensors 6 months ago the p0171 code disappeared until about a month ago.

I have check for vacuum leaks and found nothing. I have even caped off the vacuum lines to the brake booster, evap system and had no effect on the fuel trim levels. They still were very high.

Any help or further diagnosis suggestion are appreciated. I would like to stop throwing parts at it. Thank You!!!

 

Have you checked fuel pressure?

 

I have a 2005 toyota corolla with 254,000 miles on it and it also throws the P0171 code. When it does the car will run rough until I reset the check engine light. This normally only happens in cold weather and my understanding was the throttle body gasket needs to be replaced. Even though this is less then $10.00 it is fairly labored intensified. Maybe a little more then I'm willing to tear into. Buy yourself a scanner and just reset the check engine light when it comes on and everything will be fine. When the gasket is cold it sometimes screws up the air fuel mixture, but after warming up, and you resetting the computer, my car runs just fine. Hope this helps by giving you an alternative solution.

 

I'm troubleshooting this on a '00 right now. I agree check fuel pressure. Also you might consider replacing all vac hoses just 'cause:
https://www.yotashop.com/vacuum-hos...er-tacoma-vacuum-hose-kit-1996-2001-kit-1106/

(link found here on TW in the other million threads about the P0171)

 

You never mentioned if the parts you used were Toyota OEM parts or if they were aftermarket. I have *heard* that MAF and O2 sensors really need to be Toyota OEM (or Denso branded, since they make Toyota OEM), and I've always replaced mine with Denso (rather than some other aftermarket brand), including when I was chasing a P0171...

Chasing the P0171 Engine Light – ADVENTURETACO

 

I just put the least expensive MAF RA had in a '00. It was an SKP 2451095 for a whopping ~$23 before shipping. I'm not necessarily advocating for cheap parts but I wasn't entirely confident the MAF was the issue. Readings at idle were good but the most I ever saw at WOT under load was 44 g/sec which is way too low.

Anyway, for the time being the SKP is working. I swapped the MAF to cure a bucking under load rather than a P0171, however.

 

I have been chasing this code in my 96 3.4L twice in the last year. First time was a hose disconnected from the engine mounted VSV. This second time, the firewall mounted VSV had detached from bracket but all hoses still connected and resistance measurement of VSV was within specs. Tried many of the same checks and replacements as above with no luck. I recently did a smoke test by connecting the smoke hose to a port on top of the intake manifold. Smoke was pouring out the passenger wheel well area. I pulled back the w/w skirt and see smoke coming out of a tube. Anyone know what this tube is?

 

Picture of said tube would help.

 

The p0171 code is one of the more vague codes out there. For me it was a bad fuel injector. I followed this video https://www.youtube.com/watch?v=N-lhZIWOkyU and replaced all 6 injectors myself. It turned out 3 of them were cracked. I'm not saying your issue is a fuel injector, but consider it as a possibility. It could also be fouled spark plugs or even a bad MAF. The people above me have mentioned other potential causes to your issue, so consider those. Diagnose before you replace and consider checking the fuel injectors if you feel up to it. Good luck chasing your code.