I reset the codes, and lo and behold, the CEL stayed off ... through one fill-up ... until exactly 100 miles (!) later. Now it's back, with an 1131 code. I suspect the other two codes will follow.

So, I suspect that I really do have a dying heated O2 sensor. Will replace next week. Car has 81,000 miles.


Andrew
'98 Contour V6 AT
bone-stock, 85,000 miles