for some reason on the 3.1L there are two of them, the only reason I know this is because we had a car at school that the rear one broke and the techs kept replacing the one under the balancer and couldn't figure out why the flash code kept coming back..... It may not be All years but I have def. witnessed the second crank pos sensor as well...... on a side note, the rear one likes to leak oil too.... damn cheap factory parts