We do test every BerryGPS-IMU before they leave.
Can you do a loopback on the serial lines? Connect RX and TX together with a jumper cable. These is physical pins 8 & 10. And then run minicom. When you type, you should see the characters in minicom. If they dont appear, it means serial is working correctly.
sudo apt-get install minicom
minicom -b 9600 -o -D /dev/serial0
You may need to kill gpsd first;
sudo killall gpsd
Mark --OzzMaker.com --