Had a 2001 blazer motor put in my 99 blazer and the knock sensors are different.
how can I wire it up to make it run right?
The 99 only has 1 wire and the 01 has 2 wires

 

Get a knock sensor adapter to use the early sensor on the later engine in original position or screw the early sensor into the coolant hole in the side of the head and extend the wiring. Don't try to rewire for the late sensor.