Describe what a crank sensor does so I know if that's whayt I need

What kind of a problem are you having ?

I assume it's the crank position sensor. In newer cars, past 10-15 yrs, it measures the crank angle and the computer then determins valve timing and fuel injection. If car won't start or runs very erratically, consider the CPS. Depending on the vehivle, they can be easy to do or hard, expensive or not. 2005 Honda CRV, very easy fix with the unit behind the right side splash panel. $60 and a DIY job.