2001 Cadillac Deville PO335 and PO385

2001 Cadillac Deville, PO335 & PO385 which refer to the Crankshaft Position Sensor A & B Circuits. How do these faults show in the cars operation? Are the sensors inside the engine?
Here is a picture of the locations of them.
 

Good info. Thanks! Any thoughts on the operational effect when they go bad?
Not sure on Cadillac. On Fords the vehicle will not start.