I drove my truck 590 miles it ran perfect. Then 45 min latter after stoping it just won't start codes now say po320 crank potion sencer is malfunktiong so were do I find it on a 2.5 ltr and way would it just go bad for no reson is the only resone the truck won't start there is a nother code about secondary emition controls on vehicale its p1942 but I can't get any info on that one can any one please help me?

Because of the location of the Crankshaft Position Sensor to the crankshaft, and its exposure to the elements (e.g. water), they are prone to failure (quite common). It's likely mounted to the engine block, with two 10 mm bolts, off to the side of the harmonic balancer. Should be very easy to replace. Disconnect the negative battery terminal first, after recording any radio codes.

Here's what it looks like and costs:

http://www.autozone.com/autozone/catalog/parts/partsProduct.jsp?skuDescription=Duralast+/+Crankshaft+Position+Sensor&categoryDisplayName=Internal+Engine&fromString=search&itemIdentifier=233539_0_0_&productId=233539&sortType=&parentId=51-0&filterByKeyWord=crankshaft+position+sensor&isSearchByPartNumber=false&navValue=15100111&categoryNValue=15199999&fromWhere=&itemId=111-0&displayName=Crankshaft+Position+Sensor&store=1264&searchText=crankshaft+position+sensor&brandName=Duralast