Why do I lose my satellite map images on the pro + controller when I move away from my wireless network? Even if I pre cache the satellite map at home it does not reappear when flying at a different location. All I get is a poor map image with roads but little else. Also the option for cellular network is greyed out.
My Mavic Pro works fine caching maps and if I use my Airpad 2 on a separate Phantom 4 Pro remote controller everything works fine but not if I use the built in screen and remote controller.
Whay am I doing wrong?

What do you mean by "poor map image with roads"?

Do you mean you get a road map but not a satellite image?  If so, you should be able to toggle that by touching an icon on the map.

Do you mean the image is blurry?  If so, you should recache the maps but this time zoom in and out of the areas you are flying.  

I know how to toggle between the various map options and how to zoom in when looking at the composite satellite image but as soon as I go out away from a wireless connection all I see in the map window is a type of base map with roads but no detail eg coastline or other ground features. I believe it has something to do with the change in mapping provider that dji have now used. Please revert to google earth or google maps.This appears to be a fault in the android system that dji useson the built inscreen on the phantom 4 pro plus.Everythi g is ok if Iuse my other RC withmy air2.

I don't believe you are doing anything wrong, it is simply a limitation of the built-in screen. And yes, the cellular option will be greyed out because the built-in screen has no cellular connection ability.