Switching off ignition is usually also done in software. Many ECUs store data (user settings, logging and fault codes) to non volatile memory before shutting d

Switching off ignition is usually also done in software. Many ECUs store data (user settings, logging and fault codes) to non volatile memory before shutting down so the key only sends a signal. It's not a hard switch. But it could still help if all other ECUs except the faulty does shut down correctly.