Every couple weeks i had a code 1151 show up. Drivers side, front O2 xensor measuring lean condition. Sometimes this is the sensor, sometimes it is an air leak that gives the lean condition. I had seen a trace of oil around the intake manifold so i pulled it and put on new gaskets a month ago. Two weeks later, same code. Last week it was on daily. I can clear, came back the next day. Decided to pull the O2 sensor today and look at it. I removed the two bolts holding the trans shift cable so i could geet my hand up around the electric plug. Pulled it apart and saw a spot or two of white powder (contamination) on one of the terminals. I sprayed both ends with WD40, soaked, and blew out with air. Pushed the parts in and out a couple times and reassembled. Started up 4-5 times, so far no code. Something to keep in mind.