I started getting P0171 code (System Too Lean) about 2 months ago. I get one every 2-3 weeks. It always happens when I am stopped at a red light.
Since it started, my fuel consumption has been really bad. Before, it was around 21 MPG but now I do 16 MPG.
Other than that, the car drives fine (no idle problem, no loss of power)
What could be the problem?