I have used the search feature but I am seeing conflicting info. 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? I have a haynes manual but it doesn't say jack schitt about O2 sensors in detail. From what I have gathered in other posts the sensor that I need to replace is a PITA one in the rear. How easy is this to do myself or should I suck it up and have a mechanic do it?
