Activating the ignition circuitry requires power. If the vehicle has a completely dead or disconnected battery, the power must come from the diagnostic tool.
To understand the tool, one must understand Mercedes ignition logic: xentry ignition enabler
When a battery is disconnected or completely dead, Terminal 15 cannot be activated. Xentry requires Terminal 15 to be active to establish a full communication handshake with the car. The Ignition Enabler manipulates the software or the multiplexer to activate Terminal 15 remotely. Activating the ignition circuitry requires power
This is the most common version. It looks like a small plastic dongle with male and female OBDII ports. Wake-up and bus sleep states: Modern ECUs enter
While incredibly useful, using an Ignition Enabler carries significant risks if not handled correctly.