Spent hours trying to track down issue with GMU 11 (magnetometer). Found a blown fuse for GMU 11 and replaced it.....but new one blew immediately. I traced wires and from wing wiring connector to fuse bus, Wiring seems OK. Checking from connector to wing tip, I show no continuity on either power/ground pin but do measure ship voltage across same GMU 11 connector pins 7 and 9. I'm at a loss for now.
Found the issue....but can't explain it. Issue seems to be with the power and ground pins on GMU 11. A white wire and white/blue stripe. Long story short, I found the GMU 11 white wire "becomes" the white wire with blue stripe and visa versa at wing root connector. I'm 99.9% sure I used a single, un-spliced 2 wire, shielded cable between GMU 11 and wing root connector. Down stream, I connected the shielded cable wires to simple white and black wires for power and ground respectively. The fix was to switch wires at the power bus. White wire is now connected to ground and black wire to power.
Fuses stay together and GMU 11 shows up now on CANbus. Need to spend some time to configure the GMU 11 module.