i have a 2002 dodge neon sxt 5spd?

[Dillon W]

my engine light was on so i disconnected the batter the light stayed off for 2 days around 35 miles it come back on i was sittin in a parking lot the light went off it just recently come back on i cycled the key on and off the code po171 came up in the odometer i was told it might be the o2 sensor and i was wondering what you think and if it is the o2 sensor which o2 sensor do u think it is maybe the one before the cat converter i need to get my car inspected by sunday so i really need to find an answer