Originally posted by Cappuccino911:
I have a 99 contour v6 MTX. I have a p171 system to lean bank 1 code and a p1131 Lack of HO2 switch sensor indidcates lean. are there 4 o2 sensors on these cars? 2 before the cat and 2 after the cat?


Yes, there are four O2 sensors. Bank 1 is closest to the firewall, Bank 2 is next to the radiator. Upstream is before the cat, downstream after the cat.

96 Contour SE Duratec V6 24-valve 2.5L ATX 108,000 mi. Replaced: crankshaft w/ DMD, EGR valve (clogged), EVR, DPFE, PCV valve, evap emissions hose & tube (cracked), window regulator (broken), LH & RH PCV tubes, UIM gasket (leak), ignition coil