The Mercedes-Benz Electronic Ignition Switch (EIS), also known as the Electronic Ignition Starter Switch (EZS), plays a vital role in your vehicle’s security and starting system. It works hand-in-hand with the smart key to verify authorisation before enabling engine start-up. When a valid infrared key is inserted into the ignition slot, the EIS and key exchange rolling security codes. Once validated, the EIS allows communication with the Electronic Steering Lock (ESL) and Engine Control Unit (ECU), activating the ignition and starting the engine.