Check engine light error code P0171

My check engine light came on last week of course in the middle of a 200 mile road trip. I took it to autozone and they read the error code for me (for FREE). It was P0171 which means my system is too lean. Does anyone know what that means? I've heard (and read) a lot about O2 sensors, but I don't know if that is what the error means.

Any help would be greatly appreciated! My car is a 2000 G20t with only about 43k miles on it. Coincidentally the light went on the week after my bumper to bumper warrantee expired.

Thanks!

could be a ton of things MAF, TPS, O2 etc....go to www.g20.net and check the FAQs.

Carlos.