As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON HAVING AN AUDIO PANEL PARTIAL FAILURE, THE PILOT NOTED THAT THE EMERGENCY MODE DID NOT OPERATE. THE UNIT HAD MODE 4 INSTALLED. IN TROUBLESHOOTING, IT WAS DETERMNED THAT THE MONO HEADSET JACKS WERE WIRED TO THE RIGHT STEREO OUTPUT INSTEAD OF THE LEFT AS SHOWN IN THE GM4340 INSTALL MANUAL.