What does the code p1131 h02s-11 indicates lean on a 2002 Taurus 3liter engine mean?

Answer 1

It means that the bank #1 O2 sensor, the bank closest to the firewall, cylinders 1-3 is showing a lean mixture. Could be a vacuum leak, a misfire on that bank, an exaust leak upstream of the O2 sensor, fuel control or injector problem on that bank, a faulty O2 sensor, faulty PCM, faulty wiring in the engine control wiring harness, and there may be some more possibilties I haven't thought of yet.