Do not start replacing parts blindly. Mercedes electronics are expensive. Follow this workflow:
Attempting to "download a random file" without understanding the vehicle's VIN, immobilizer password, and RSA encryption will brick your EIS permanently.
A wiring issue between the EIS (behind the steering wheel) and the ECU (under the hood) can block the "Start Release" signal. Check for rodent damage or corrosion in the engine harness.
A failing key transponder chip or a broken antenna ring around the ignition barrel will disrupt code transmission. Software Solutions: Using Start Error Repair 1.3
