I purchased a a Phantom 2 +at the end of November.

I have had several successful flights, but a few days ago, the Phantom decided to fly home, even though there was no battery warning (that I had seen before on prior flights). The flight started with a compass calibration and 6 or more satellite lock.

The Phantom ended up flying into some trees and fell through the tree about 20 - 30 ft. The rotor guards broke, and a couple of props were damaged. After removing the prop guards and and replacing the props, the Phantom appears to fly well, but I can not get a GPS lock.

What can I do to to troubleshoot the GPS?

Thanks

Can you open the shell and see if the GPS cable is disconnected?
Also you could inspect the GPS unit itself (on top, under the insulation) and see if it looks ok.

If the GPS cable is disconnected the motors want spool up, but perhaps a loose connection.

Increase RTH altitude, mine is 150 feet.

The GPS antenna is ceramic and most likely cracked in your crash. You can check it by removing the top boby half. Under the large piece of foil tape is the GPS unit. It is attached with 4 small screws. You need to remove that to check the antenna. If it is cracked, you need to replace it. You can get a complete GPS unit for about $165.00 or just the ceramic antenna for about $4.00 if you have the ability to do that.