thanks again...

but what does ac, + natural plug mean? and how do you know its the right pin?

the discription reads

07 suburban

 

Speed Sense yellow/black ac ECM, black 73 pin plug, pin 57

 

The ECM (Engine Control Module) is on the driver side fender, behind the headlight.

 

Reverse Light dk. blue + BCM, natural plug, pin 22

The BCM (Body Control Module) is to the left of the steering column.