This is what my search found:

P1131
is the rear bank(by firewall) upstream/ before the cat. HO2S11! it is a indicates lean code but if your car runs good still you should replace that O2 sensor(HEGO). and i would recommend replacing both upstreams with bosch to $60 a piece.

Is that what you were referring to?

Thanks a million!
~Anna


1998 Contour LX V6 2.5L