Toyota Repair: code PO 171, air flow meter, phillips screws

Question
I replaced the rear O2 sensor on my 2001 V6 Toyota Tundra with a new Bosch 13980, purchased on the internet. Within 50 miles, while towing a trailer, my check engine light came on (code 171-lean fuel condition). My question is could this new code be the result of an improper or faulty sensor or is this just coincidental. The truck towed fine, except at around 70 mph any rapid increase in gas would cause the engine to drastically bog down.

Answer
O2 sensors don't cause the PO171 code, there is an airflow meter on the intake tube just downstream from the air filter, it's mounted on the side with two small phillips screws, the way to fix the 171 lean code is to remove the air flow meter and clean the inside of it with an electronic parts cleaner spray, do not use anything else, make sure that it gets into the inside openings where the platinum air sensing wires are, let it air dry and reinstall it, disconnect the battery and wait at least ten seconds, while your'e there check the air filter and if needed replace it.