It is cut right after the o2 sensor hooks up do I need a whole new harness?

 

If it is just the O2 sensor harness that has been cut, find a car in the yard and cut off what you need. Solder gun, patience, and some shrink tubing.

 

The problem is that it is cut after the o2 sensor hooks up the engine harness is cut not just the o2 sensor

 

if ur able to cut some of the harness wrapping, do that and see if u can find the same wire that is cut and splice into it and make a new connection with it. like mad mike said, soldering gun and shrink tube to make it's as water proof as possible.

 

How much does that throw the sensor signal off?

 

Yes, thus.
Cut the part off a yard car that you need.

 

it always tells it that the engine is running lean