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WORLDWIDE DHL SHIPPING · BENCH-TESTED · 1-YEAR WARRANTY
WORLDWIDE DHL SHIPPING · BENCH-TESTED · 1-YEAR WARRANTY

Mercedes-Benz EZS/EIS Module Repair

Won't your Mercedes start, or does the key not turn? The problem may be in the
EZS module (Electronic Ignition Switch).

At Ecumotorstock, we are experts in the repair and reprogramming of EZS / EIS modules, fully restoring the starting and immobiliser system of your Mercedes-Benz vehicle.

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Precise diagnosis

We identify faults in EZS modules with advanced technology.

Professional repair

We restore the EZS for safe and reliable starting.

1-year warranty

Your EZS module repaired as good as new, backed by quality.

Reliable service

More than 15 years repairing vehicle electronic components.

What is the EZS / EIS module and why is it so critical?

The EZS module (also called EIS) is the electronic ignition system of
Mercedes-Benz vehicles.

This component:

  • Manages the reading of the electronic key
  • Controls the immobiliser system
  • Activates the ignition and allows the engine to start
  • Communicates with the ECU, ESL (steering lock) and other electronic units

When the EZS fails, the car can be left completely locked, unable
to start, even if the key is original.

Main causes of EZS module failure

Main causes of EZS module failure

Internal wear of electronic components: the passage of time and intensive use can damage microchips and solder joints.


Battery problems or unstable voltage:
voltage spikes can damage the EZS memory.

Moisture or corrosion: especially in models with sealing problems or leaks.

Software errors and failed updates: a failure while programming can corrupt the internal EEPROM.

Incorrect handling: Inexperienced repair attempts can make the problem worse.

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Symptoms of a faulty EZS module

Symptoms of a faulty EZS module

If your Mercedes shows any of these symptoms, the EZS may be failing:

  • The key does not turn in the ignition
  • The engine does not start, even though the key is original
  • Keyless-Go system failure
  • Doors do not respond to central locking
  • Immobiliser light on
  • EZS-related error messages on the instrument cluster
  • Error codes B1676, B1677, B1679, B1691, B1692
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Mercedes-Benz models affected by EZS failures

Mercedes-Benz models affected by EZS failures

We have repaired EZS modules in dozens of models, including:

A / B / C / E / S-Class / CLK / SLK / ML

  • A-Class: W168, W169
  • B-Class: W245
  • C-Class: W202, W203, W204
  • E-Class: W210, W211
  • S-Class: W220, W221
  • CLK: W208, W209
  • SLK: R170, R171
  • ML: W163, W164

These vehicles share similar EZS modules and suffer frequent failures after 8-10 years of use.

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What does our EZS module repair include?

At Ecumotorstock we offer a complete service:
✅ Electronic diagnosis of the EZS/EIS system
✅ Reading and cloning of the internal microprocessor (MCU or EEPROM)
✅ Repair or replacement of damaged components
✅ Bench function tests
✅ Reprogramming and synchronisation with key and ESL
✅ Return of the module 100% functional with warranty
In many cases, it is not necessary to replace the original module, which saves hundreds of
euros and avoids coding errors.

Most common EZS references we repair

Most common EZS references we repair

These are some of the most affected EZS references:


203545018, A6395452108, A2045450908, 2095451308, 1699051500
2095450508, 2155450808, 6395450108, 2115451408, 2045451308
A2075450108, 207905260, 2105450008, 6395450208, 1695451908
A2129055600, A6395450608, 2205450008, 1695451108 and more.

Can't see yours in the list? Write to us and we will check it straight away.

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Won't your Mercedes start because of an EZS fault?

Won't your Mercedes start because of an EZS fault?

You don't need to go to the dealership. Send us the module, we repair it and return it to you ready to fit.

You can also bring your car to our workshop if you prefer.

Talk to a technician on WhatsApp → Open WhatsApp

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Why choose Ecumotorstock?

🧠 More than 18 years in automotive electronics
️ Technicians specialising in Mercedes-Benz
📦 Nationwide service: collection and delivery with MRW
🔐 Repairs with a genuine warranty
⚡ A faster, cheaper solution than replacing the module

Frequently asked questions

Can I send just the EZS module?

Yes, but we recommend also sending the electronic key so we can check the
synchronisation.

Can the EZS be repaired if the car won't start?

Yes, it is the most common case. The module arrives locked and we restore it on the bench.

Can I bring my Mercedes to your workshop?

Of course. We have specialised technicians for fitting and removal if you need it.

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