Crank shaft sensor Bolt off in the block?

It's a common thing but to install the new sensor you need to remove the broken off piece of bolt. The first step in this is to plug the hole the sensor goes into then try the removal methods. To do that you will need to either drill out the broken piece so an extractor can be used or use a welder to weld a nut to the piece to remove it. The second one usually works better because the heat during welding tends to break any corrosion loose so the threads release.

This video shows a few methods of removal:

https://www.youtube.com/watch?v=x_ky5JVxtqU

Once you have the broken bolt out you can replace the sensor.