For several years, my 2017 Fit has had an electrical issue that manifests as a phantom battery drain. I have finally pinpointed the circuit. The Audio-Navigation circuit (the only component connected to the 15A fuse [21] in the left side fuse box under the hood) is causing the issue. There is a 79-80mA draw in that fuse when the vehicle is powered off. Often, I need to jump-start the vehicle, even though batter(ies) are new and the alternator shows it is charging. With fuse 21 removed there is no power draw, but other systems (door locks, side-view camera, etc.) do not work. When the vehicle is started without the fuse in place, the car ONLY starts with the key fob against the start button. Reinserting the fuse allows the vehicle to start, doors to lock/unlock, etc., and there is NO power draw...unless the Audio-Navigation power button is pressed and held for 2-3 seconds. When that happens, the power draw occurs with the vehicle powered down.
It appears that the Audio-Navigation system may need to be reconfigured/recoded/replaced (not sure which) to resolve this issue. Ideas??

Vehicle after sitting overnight--powered OFF. Headlights on (often blinking)

Same morning, instrument panel on, but the vehicle is OFF. Start button will not start vehicle. Weird...

 

Turns out I was right...kind of. Service Department arrived at the conclusion that my Fit needs a new Smart Power Control Unit (basically, the card that operates the Audio-Navigation component). At $600+ (parts) and $500+ (labor), I think I can drive the vehicle (120k miles) like those I drove in the '70s...