Auto Parts: transmision, fluid leak, ecm

Question
06 yuon 4x4 will not shift into 3rd or 4th gear could it be a sensor

Answer
    I suppose it could be, but I don't know which one.  If you are not getting any codes (check engine light) then the only likely culprit is the ECM.  I am assuming that there is not a fluid leak, of course.  You are going to have to get a tech to scan the ECM and look for the problem.