Yes, need a tester. The fact the center light works means the brake switch is good. On this gen/model the "outer brake" lights go thru the failure sensor but not the center/high mount light - it comes straight from the switch ???

The outer lights do share a common ground (G601) so that is in "play" as well. So knowing if there is good ground and then knowing is there is power (12v) on the green wire out of the failure sensor will be the next step.

 

It was a loose wire coming out of the little box in back... its working now... thank you all!!