Lean Bank 2 (driver's side)
If that is the only code suspect either a MAF problem, vac leak, or O2 sensor problem. This is when a data tool is most useful.
Compare both bank's O2 readings, and fuel trims and crosscounts. If both sides trim lean under load, suspect MAF. If lean at idle, look for a vac leak. If only one side is trending lean while the other is even, suspect an O2.
A bad MAF can cause one bank to code as in any system with that many miles will have one O2 sensor a bit lower in voltage, and slower on crosscounts than the other. A fuel pressure or MAF problem effects all cylinders the same, but the weak O2 codes first so people/idiots/shadetrees throw a sensor at it first only to throw another sensor on the other bank a few hundred miles later when that one codes.