I recently took my 1996 Contour SE (V6, mtx) to have a CEL diagnosis. The code showed a bad front O2 sensor, so the shop replaced it.
The light went back on within a few miles, so back to the shop it went. Same code on the brand new sensor. My mechanic did a little detective work, and believes he discovered a conflict between the wiring diagram and the computer. So he replaced the rear O2 sensor instead, even though the code was pointing to the front O2 sensor, and the problem went away.
So he says either the computer is indicating the front sensor when the rear sensor is bad (and, by extension, vice-versa), or the wiring diagram is wrong.
Has anyone else ever experienced anything like this? Thanks.
