rap is not working, is this a sensor or fuse.

The RAP system in your 2004 GMC Envoy is pretty complicated. The body control module (BCM) determines if RAP functions should be present based on door inputs, battery capacity, and a 10 minute timer. My first question would be do the power windows work when RAP should be active. If they do then the BCM is turning on the function and the fault may be in the radio. If the windows don't work either then the fault is most likely with the BCM or one of its inputs.