Land Rover Repair: O2 Sensor Fault Code 1171, land rover discovery, air flow meter

Question
I have a 1999 Land Rover Discovery II. Recently the check engine light came on. The fault code is 1171. This is listed as:

"P1171 Oxygen Sensor System Too Lean Fault Banks A & B"

Does this mean I need a new Oxygen Sensor? It says "A & B" Does that mean there is more than one O2 Sensor I need to replace?  

Answer
There are two oxygen sensors, but 1171 is just lean on bank 1.  Usually, code 1171 comes up in conjunction with 1174, which is lean on bank 2.  These codes relate to air flow.  Normally, when these two codes come up together, there is also a transmission gear ratio fault.  This combination indicates an air flow meter fault, indicating you need a new air flow meter.