I just installed the avic-d3 and GEX-P920XM, but its like when i start the car it is picky if its going to see the GEX-P920XM or not. I have checked the ground and power source. The data cable is firmly in place. If i unplug the unit and plug it back in then the avic sees it. Any suggestions?

make sure the cable is not reversed. black plu to black port of xm. blue plug to blue port of avic

Check the crappy fuse holder too. Too many times I've seen that fuse holder partly break which causes the same problem you're describing.