should be on left side of engine toward the back, in the side of the block, down under the fuel filter area if im not mistaken, at least that was where it was on my 2000. And im guessing your having the check engine light come on and then after a few days it goes away then suddenly appears back on while driving. Mine was very hard to get to, the starter has to be removed ect to get up at it, also mine was welded basically into the block, its plastic but i think at the factory someone fell asleep and forgot to use some antiseize, it had to be tapped with a long sheet metal screw and then pulled because it broke in half... . hope this helps. Do a search mine should pop up where i had it to go bad.