P0171 Engine running too lean

I feel your frustraton! FYI, I have a mech friend with the diagnostic device that reads these codes. Brought my 2000 4Runner to him with the same P0171. We were able to reset my light. Suspect the cause of my problem was the engine air filter box; the cover had popped ajar at some point (which was likely causing too lean a fuel/air mixture).

Important part is this; I was able to sit with him as the computer read, page by page, through the codes and diagnostics. If nothing else, I gained peace of mind as each page of diagnostics showed the engine performance to be "OK", to include 'pending' problems. All this was done in a matter of minutes (ever wonder how long most mechs ACTUALLY devote to your vehicle in most cases!). If you have a trustworthy mech, I'd recommend asking him if he'll allow you to review the diagnosis with him, and have him tell you page by page what's good with the car (and what's not). Otherwise, you'll remain in the shroud of mystery every time the light comes back-- and pay them a hefty some on EACH return (like so many before you). Hmmm. Get it!

Lastly, the diagnostic device (known sometimes as an OBD2) costs as low as $65, is 'plug & play', and is universal for any auto. If you're reading this email, you probably have enough 'tech-savvy' to operate it. Keep this in mind on your next trip back to your mech for the same repeat gripe!

Thanks for the response, guys. I will be looking into purchasing my own diagnostic device.
My father suggested that this problem might be caused by a bad/worn-out/gunked-up fuel filter. Since that wasn't ever mentioned in my manual, or any internet research that I did, it makes me wonder, but the relation to fuel pressure makes it viable.
Has anyone come across a bad fuel pump as a cause for a P0171 error code?

Starts great. When in gear and gas given vehicle will hardly go and minor back fires then when it warms up no back firing and will acclerate good but has a hesitation. When computer is hooked up it says system lean bank one. I have done a tune up and fuel filter still no better. Please help

92 runner 197k miles v6 4x4 manual trans

needs a oil change. Thats a given.

**running rough notice the cat was cherry red. So the morning I got it replace then took over to a shop

code 71 egr connection malfuntion =which is the green wire from the connector is pulled out. So that triggers the CEL

Knock Sensor Code 52 no signal

so the job that they did was remove and install platium to clean connectors to injectors (they said 2 was not connected)
engine compression.180 all around. Replace spark plugs

ignition timing adjustment. This was all that was done

still seem to be something wrong.

I took it to a previous shop before it ran rought they noted that the "transducer hose" to the throttle body was clogged and need to be replace or unclogged I have no idea what is the transducer hose or where it is located and how to replace

another question would be if the AirFlow was faulty could this be a reason why a overheater cat. How to check it?