Camry Forums - Toyota Camry Forum - PO171 in 2005 Camry - how lone does it take the code to come back?

(Note, in the forum title make that "long" not "lone" -- I screwed that up but cannot edit it unfortunately.)

Hello,

We have a 2005 Camry LE (2.4L, 4cy. 5A. The "check engine light" is on and the code is P0171 ("System Too Lean, Bank 1"). My Bludriver OBDII code reader and app tells me: “This is one of the most common problems for your vehicle. The oxygen (O2) sensors are
detecting a lean condition, which means there is too much oxygen in the exhaust (i.e. air
is getting into the engine through a leak or the O2 sensor has failed).Before replacing
the O2 sensor, check all other possible leaking components.Using the Live Data function
of your scan tool, you can check the short-term and long-term fuel trims to narrow your
troubleshooting (normally both should be close to zero).If the short-term is over 15% at
idle and drops at higher RPMs, you likely have a vacuum leak. If the short-term is close
to zero at idle, and increases at higher RPMs, you likely have a Mass Air Flow sensor or
fuel issue.”

I followed their suggestion regarding using the “Live Data” function. Longterm was at about -5.5% at idle and stayed their even when revving the engine.

Short-term was at -3.1% and when I revved the engine it would move, but then adjust to relatively close to that. I cleaned the Mass Air Flow sensor, and short-term initially went to -9.4%, but then returned to -3.1%.

I am going to put in a new engine air filter. Also, I cleared the code.

QUESTIONS: If what I am doing doesn’t work, now long until I can expect the code to pop up again? Will it be pretty immediate, or can I expect it to take 40-50 miles of driving?

Also, any other suggestions as to how to proceed? I don’t see any obvious vacuum line leaks…

Thanks!