My wife's '99 Buick Century Special 3.1L engine, 40k miles, has been running rough and throwing codes P0101 (MAF Sensor Performance) and P0171 (1/1 Fuel Trim System Lean). I know 1/1 means upstream O2 sensor of the rear bank.
I have a www.alldata account on this car, and the troubleshooting flow chart on P0171 says to take care of any other codes before troubleshooting that one. I don't have a scan tool.
S-o-o-o - My questions are: (1) Of all the likely probabilities, based on experience, what is *the* most likely root cause? (2) What are some simple tests to eliminate certain possibilities and narrow it down so that I can avoid a shot-gun trial-and-error mode (i.e., replace O2 sensor, problem still there, so replace MAF sensor, maybe still not fixed, etc)? (3) Any good GM- or Buick-specific web-based forums to post this to?
Thanks a lot for any help.