I had purchased the PIX and discovered on maiden flight there were issues with the gps. I did not trust the module , so I removed the PIX and replaced with other , That was about 3 years ago. My question, is there anyone out there that repairs/troubleshoot GPS problems with the PIX ?
in the meantime, the GPS is configured automatically, by the pix with an actual firmware and there are plenty of status messages through mission planner.
You can diag the module with the ublox u-center in an passthrough mode or with a serial adapter cable.
It is relatively save to fly it in non position modes (stabilize, alt-hold) to get further infos from log files and telemetry.
With more of this information there should be someone who can help you.