Audio System Symptom Troubleshooting - Radio preset memory is lost

Radio preset memory is lost Inspect the under-dash No. 6 (10 A) fuse. Is it OK?
YES | - | Go to Step 2 .
NO | - | Replace the fuse and reset. If it fails again, repair the short to ground in the harness.■
Remove the audio-HVAC display module. Turn the ignition switch ON (II). Measure voltage between the audio unit connector A10 terminal and body ground. Is there battery voltage?
YES | - | Go to Step 5 .
NO | - | An open wire between the under-dash fuse/relay box N11 terminal and audio unit A10 terminal.■

Check for continuity between the audio unit A20 terminal and body ground. Is there continuity?
YES | - | Faulty audio unit.■
NO | - | An open wire between the audio unit A20 terminal and body ground (G504).■
Operate 1 of 6 preset switches to see the symptom appear. Does the symptom appear?
YES | - | Faulty audio unit.■
NO | - | Operation is normal.■