Chestnut cigarette-power connection delays vehicle shutdown on 2021 Genesis G80

### Describe the car bug

Vehicle / hardware
Vehicle: 2021 Genesis G80 (RG3)
Hardware: Chestnut, powered from the vehicle cigarette-lighter / accessory socket
Problem

When the ignition is turned off while Chestnut remains powered from the cigarette-lighter socket, the vehicle does not shut its electronics down normally right away.

The navigation/infotainment system remains on and a message related to checking/requesting the gear selector (shift lever) status appears.

Reproduction / observations
Chestnut connected and powered from the vehicle cigarette-lighter socket.
Turn the vehicle ignition OFF.
Navigation/infotainment remains on temporarily and the gear-selector-status message appears.
Disconnecting the USB connection between Chestnut and the comma device does not change the behavior.
Disconnecting Chestnut cigarette-lighter power causes the vehicle to shut down normally immediately.
If Chestnut power is left connected, the vehicle eventually shuts down after roughly 5 seconds.
Expected behavior

The vehicle should complete its normal ACC/ignition shutdown sequence immediately when the ignition is turned off, regardless of whether Chestnut remains connected to the accessory socket.

Additional note / possible cause

Because USB disconnection has no effect while removing the 12 V Chestnut power immediately fixes the issue, this appears more likely to involve the Chestnut power path / shutdown transient than the USB/CAN data path.

One possible explanation is residual energy or reverse-current/backfeed from the Chestnut power supply / DC-DC input path after the vehicle cuts accessory power. This is only a hypothesis at this point; the voltage waveform has not yet been measured.

It may be worth checking the Chestnut vehicle power cable / power stage for reverse-current blocking, input isolation, or active discharge behavior, particularly with Hyundai/Genesis accessory-power circuits.

### Provide a route where the issue occurs

google_101244957514052970483

### openpilot version

0.11.1

### Additional info

_No response_