2.3L ('02-'11) Truck threw code P0171 - (likely replace O2 sensor)

[Garth Libre]

My 2010 4cyl (manual tranny) Ranger just threw Code P0171. The Truck still idles normally, performs normally and seems to not be using any more fuel. The light is still on of course. Code P0171 indicates : TOO LEAN. The computer spits back a too lean code is usually O2 sensor bad --- or MAF (mass air flow sensor) bad or bad fuel filter.

Now I changed the fuel filter two years ago so I suppose it could be a problem however that leaves O2 sensor or the Mass Air Flow Sensor (which I just cleaned a little more than a year ago with the recommended sensor safe cleaner while the engine was running.). There are two O2 sensors according to the book. Do I change both sensors since they are only $20 each? Is one more likely to be the problem?

 

[Curious Hound]

I would clean the MAF sensor again, replace the fuel filter, check fuel pressure and maybe even check for vacuum leaks.

Personally, I believe the sensor first and narrow down the logical explanations. The sensor is telling you the engine is running lean.

Think about it. When your fuel level sensor tells you you're out of fuel. Do you replace the sensor ? Or put fuel in the tank.

Don't shoot the messenger before you know whether he's telling the truth or lying.