Every Tesla needs its low-voltage battery to unlock the doors, wake the screens and close the contactors that connect the main pack. When it fails, the car looks completely dead even with a full traction battery. Cars built until around late 2021 use a 12V lead-acid unit, an AGM type on Model S and Model X and a compact maintenance-free one on Model 3 and Model Y. It sits beneath trim panels in the front boot area.
Later cars switched to a lithium low-voltage battery of about 16V, and the Cybertruck runs a 48V system. Those are Tesla parts fitted by Tesla service, and this service does not replace them. What can be done at the car is a test, a like-for-like 12V replacement on older models, and an external 12V supply to wake a car with a flat low-voltage battery. The traction pack itself cannot be jump started. An empty pack means recovery to a charger.