Exhaust Brake Squeeeeeeel
 

This just started happening. When I push the exhaust brake button and slow to use it , I hear a high pitched SQUEAL. Then when I push the button to off it stops. Any ideas?

Exhaust leak up stream of the exhaust brake.

How do I fix that?

I would find the leak first, it may just be something that needs tightening. If the squeal is loud enough you should be able to pin point where it's coming from.

You might see a small whisp of soot by the leak too.

What they said. Just follow the path of the exhaust piping before the EB and look at it carefully.