Bad oxygen sensor? Or something else? Help?!

I have a 2004 Honda Accord DX, I have gotten a P0171 error code(Fuel System Lean), and P0131 (o2 Circuit Short to Ground).

My car runs fine once its started and I haven't noticed any gas mileage problems, but when I start it its a rough start and takes 3-8 secs to turn over.\

From my understanding this cant be the O2 sensor because it is in play when starting the engine.

I have been looking everywhere online and only thing i could find at all is to maybe check the some other sensors?

Can these sensor be check with a multi-meter? If so which ones and where? I check the battery and it is fine. Some type of fuel sensor?

I don't want to waste money on buying a oxygen sensor if this really inst the case.

Please help I am a newbie!

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