P1151 is upsteam bank 2 sensor (to the right of oil filter on left side of exhaust manifold), see CEG FAQ section re codes:
http://www.contour.org/FAQ/FAQ.cgi?s=probs&display=checkengine

HO2SXY
HO2S=heated oxygen sensor
X=bank(1,rear;2,front)
Y=sensor(1,upstream:2,downstream)

98 Mystique LS v6 atx 110,000km
97 Contour LX v6 atx 125,000km
stock CD on LS, cass on LX
spoiler, tinted windows on LS only
4 wheel discs on LX only
All other available options on both