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Secondary 12v source operating after 12v lead acid and HV battery disconnected-21 amp drain aft

Wondering what in M3SR+ 2021 is drawing 21 amps at 13 volts after the car is powered down on safety menu. Activated 4 immersion speakers. Found that MCU2 is powered even after 12volt battery disconnected and HV connector disengaged. Planning a rear amp and subwoofer installation. Why would MCU2 lights inside panel remain on after LV and HV batteries disconnected? Where would a second 12 volt source be located and why would MCU2 need continuous 12v after Electrical penthouse disconnected?
Maybe there's a flux capacitor installed somewhere?

Just curious: How did you determine the amount of current that was being drawn after disconnecting the low voltage (12V) and traction (HV) batteries? That implies you were interrupting a voltage connection in order to install an ammeter. Or did you use a clamp?
Good point. Back to future. I’m looking for flux capacitors…No problem

Seriously, two different observations. Current monitoring from Tesla Service menu. Display not identifying where the current draw from. In this case 12v and HV connected as normal. Selected power down from menu with everything turned off with butt in drivers seat.

Second observation. After disconnecting 12v terminal from battery, I rubber bagged the positive terminal and disconnected the HV contractor. In this case, I had already powered down the car on the safety menu. I observed the lights behind the dashboard at the computer (red colored) were still illuminated. I presumed a secondary power source as small guage pink wire from battery through firewall along the passenger side floor panels to near penthouse (HV connector) was continuously powered. I didn’t have my clamp ammeter to capture the current at various locations. Next time I’m gonna repeat the same conditions to determine the circuits running with and without normal connections of low and high voltage circuits.

I want a baseline of voltage and current loading off the 12v battery before installing a rear amp to power subwoofer and/or rear deck speakers.


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