Pontiac Grand am 2002. Trouble code P0171?

[POST 1036]

Recetly my car started acting up after i had driven about 1 hour. Than the engine light came on. i plugged in my code reader and it pulled out the code p0171. It means bank 1 system to lean. How would i go about fixing this? i also have the code P0420 meaning catalysy system below threshhold bank 1. Would replacing my o2 sensors fix the problem or what? Any help would be great

 

[mdcbert]

TOO lean..Like it is lean too much..Not like :heading to "lean".
replace the "first" O2 sensor first, that will regulate the "bank 1" mixture and probably correct the catalyst issue.

The computer uses the first O2 sensor to "read" the mixture, when it goes bad.. it tells the computer "hey, left side is lean".. then the computer richens the fuel mixture...then the cat cant burn off the excess...then the second O2 sensor says "Hey this is rich" and puts out another code.

Change the first one first, clear, then see what happens.