O2 sensor - rpms not running consistantly
 

2005 taurus. Runs rough, will cut off on you.
The current codes are P0174 (system to lean bank 2) and P2197 (O2 sensor stuck lean bank 2 sensor 1)

The sensor has been replaced twice. After each replacement the car runs okay for about a 100 miles then goes back to the same problems.

What else can cause the computer to throw code P2197?:confused: