What are EZS and EIS, and are they the same? What are the common symptoms of failure?

The terms EZS (Elektronische Zündschloss) and EIS (Elektronische Zündschloss) both refer to the electronic ignition system in Mercedes-Benz vehicles, but they are used in slightly different contexts, especially across different models and years.

1. EZS (Elektronische Zündschloss) – This term is typically used in older Mercedes-Benz models, particularly those from the late 1990s to early 2000s. EZS refers to the Electronic Ignition Switch system that manages keyless entry and ignition functions, including communication with the engine control unit (ECU) to start the vehicle.

2. EIS (Elektronisches Zündschloss) – In more recent models, Mercedes uses the term EIS, which stands for **Electronic Ignition Switch** as well, but the systems are more advanced and integrated with the keyless-go systems. EIS manages the start/stop of the engine, immobilizer functions, and allows for features like push-to-start or keyless entry.

Key Difference:
- EZS is typically used in older systems, whereas EIS is used in newer models with more advanced features.
- Both systems perform similar core functions of controlling the ignition, anti-theft protection, and vehicle access, but EIS usually incorporates more modern technology and integration with the vehicle’s security and convenience systems.

Mercedes-Benz may use both terms interchangeably depending on the model year or system version, but in general, both refer to the vehicle's **electronic ignition and security system. The terminology change likely reflects the evolution of the system over time, with EIS representing a more sophisticated, modern version.

The Electronic Ignition Switch (EIS), also known as the EZS (Electronic Zündschloss), is a critical component in Mercedes-Benz vehicles for ignition and key recognition.

Common Electronic Ignition Switch (EIS/EZS) failure symptoms on Mercedes vehicles include:

1. No Ignition Power (Terminal 15 Issue): The engine may fail to start or turn over due to a lack of ignition power reaching the necessary circuits.

2. No Communication with Vehicle Modules: The EIS may fail to communicate with other car systems, resulting in error messages or the inability to start the car, as the key and EIS cannot exchange information properly.

3. Failure to Recognize the Key: If the EIS fails to recognize the key, the car will not start, and you may see a "no key" or "key not detected" warning.

4. No IR/Coil Activity: The infrared (IR) or coil signal used to read the key’s electronic information may not be functioning, preventing the key from being recognized and the car from starting.

5. Immobilizer Activation: A malfunctioning EIS can cause the immobilizer to stay active, even with the correct key inserted, preventing the engine from starting.

6. Intermittent or Inconsistent Starting: The vehicle may start intermittently or fail to start altogether, even though the key appears to be working, indicating a possible issue with the EIS or key programming.

7. Dashboard Warning Lights: A faulty EIS may trigger warning lights such as "EIS error" or "Immobilizer," or the car may display a “Start Error” message.

8. Key Won’t Turn in the Ignition: The key may become stuck or fail to turn in the ignition, indicating a mechanical or electrical issue with the EIS.


If you are experiencing any of these symptoms, you can send your EIS along with the key to us for testing. In some cases, we may need additional parts to fully diagnose the issue. Please feel free to contact us directly or submit a New Order form on our website for further assistance.


Common Mercedes-Benz EIS/EZS Part Numbers:
For W164 ML-Class (2006-2011):

A164 545 08 08
A164 545 14 08
A164 545 15 08
A164 545 18 08
A164 545 22 08

For X164 GL-Class (2006-2012):

A164 545 08 08
A164 545 14 08
A164 545 15 08
A164 545 18 08

For W251 R-Class (2006-2013):

A251 545 08 08
A251 545 14 08
A251 545 15 08
A251 545 18 08

For W216 CL-Class (2007-2014):

A216 545 08 08
A216 545 14 08
A216 545 15 08
A216 545 18 08

For W221 S-Class (2005-2013):

A221 545 08 08
A221 545 14 08
A221 545 15 08
A221 545 18 08

For A164 (ML-Class, GL-Class, G-Class):

A164 545 08 08
A164 545 10 08
A164 545 11 08
A164 545 15 08

Other Notable Part Numbers (Specific Models):

A221 545 26 08 (S-Class, newer models)
A164 545 16 08 (for specific ML and GL-Class)
A221 545 40 08 (for certain S-Class vehicles with Keyless-Go)
A164 545 12 08 (for certain models with specific ignition configurations)