My 99 metro has a diagnostic code that is P0172. "Fuel trim bank one condition", what does this mean?

Is it using too much fuel?

What this means is that feedback is saying the engine is running too rich (lots of gas, poor mileage maybe?)

First a quick lesson: The MAF is the mass air flow sensor. The O2 sensor senses O2 in the exhaust. The injectors put gas in the engine and the pump pumps gas.

The MAF senses how much air is going in and the CPU adjusts how much gas is needed. If its bad it could use too much gas. If the O2 sensor is bad it could run rich as well. The O2 sensor is used to monitor how much O2 is in the exhaust, it it thinks there is too much O2 it adds gas. the injector and pump just deliver the gas, not much chance its those.

If it is using too much gas it's probably the O2 sensor. Check to ensure the wire to the O2 sensor is not broken. If it is it runs rich all the time (more gas) Same for the MAF though.

If it isn't that then maybe the injector. They aren't too tough to swap out. My too tough and your too tough might be different I guess.

Anyway it could be opening too far or not closing all the way, but that's more rare. Go for that sensor.

This is all very interesting and wonderfull, but it really does not change a thing. "What will be, will be" Man can only surmise and wonder. Spiritually! your guess is as good as mine. It makes good reading tho! I am not going to get excited about this as some kind of omen. "Limited in his understanding and experience by his five physical senses, man compared to God is little better than an insect. His world exists for only a small distance in any direction, and yet he considers his opinion enlightened in all directions." God has given us some clues as to what to expect in the latter days. Do what He advices us to do and don't worry. It is all in His hands anyway!