mercury cougar black smoke problem on 2002 Mercury Cougar

My 2002 Mercury Cougar has black smoke coming out the tail pipe when idle at times and when accelerate hard service engine light is on code reads po401 replace 02 sensor down stream @ back of car it don't run rough at all.

by in Shellman, GA on March 28, 2014
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1 answer
ANSWER by , March 28, 2014
See other post.