Hello,
I have been having this problem for month now autozone did free scan came up po171 they told me check oxygen sensors plus book says this. I replaced both upstream and downstream with correct ones and cleaned maf sensor and when reconnect battery stays off for like day. I took it back check codes again still same he said i had to clear codes from memory and he did this with scanner everything fine 2 days later light on again. grrrrrrr first trans had be rebuilt now 2 days after that been dealing with this cel.. Seems be running better after changed o2 sensors however still getting cel any other thoughts?? 98 ford contour se 4cyl thanks
