Did a quick search on the forum and only found a few hits about this code and O2 sensors. The problem is that about a year, maybe little more, ago I replaced this sensor because I was getting this same P0150 code over and over again. After replacing everything has been fine until about 2 weeks ago and now it is the same thing. Clear the code and comes back constantly. There are no other codes that pop up with it. Has anyone had a similar issue? What could be causing this other than a bad sensor? Any help is appreciated.