What Is Mercedes EIS Cloning, and When Do You Need It?

If you've been told your Mercedes needs a new ignition switch, you may also have heard the phrase EIS cloning. It sounds technical, but the idea is simple: instead of starting from scratch with a blank switch and new keys, the data from your original switch is copied onto a replacement so the car, and your existing keys, carry on as before.

Here's what the EIS does, what cloning involves, and when it's the right fix.

What the EIS Does

The Electronic Ignition Switch (EIS), also called the EZS (Elektronisches Zündschloss) and labeled N73 in Mercedes documentation, is the slot where you insert your key on most 1999 to 2014 Mercedes-Benz models. It's far more than a switch. It acts as the car's security gatekeeper:

It reads the encrypted code from your key and decides whether the key is valid.
It stores the car's identity data, including the VIN and the records for each key paired to the car.
It tells the electronic steering lock (ELV) to release, and waits for confirmation.
It authorizes the ignition and starter only once the key and steering lock check out.

On cars with the FBS3 security system and the infrared SmartKey, which ran on many models through roughly 2014, each EIS holds a limited number of key positions (commonly eight). Some models moved to the newer FBS4 system before 2015, so the year alone doesn't tell you which system a car has.

Signs Your Ignition Switch May Be Failing

No key works, including a spare that used to.
The key won't turn, or it turns and the dash stays dark.
The key sticks in the switch or is hard to remove.
The problem appeared after the battery went flat or after electrical work.
The car starts intermittently, more so in heat or cold.

These signs overlap with steering lock and key faults, so testing comes first. If you're not sure which part is to blame, start with Mercedes key turns but nothing happens: ELV vs EIS vs key.

What EIS Cloning Actually Is

Cloning means reading the data stored in your original EIS and writing it onto a compatible replacement switch, usually one with the same part number. That data includes the car's identity and the key records, plus the pairing that lets the switch work with other modules such as the engine computer and the steering lock.

When cloning works, the replacement switch behaves like the original. The car recognizes it, and your existing keys keep working because their records came along with the data.

Cloning vs Starting Fresh

The alternative to cloning is fitting a new switch and having it set up and paired to the car, often with new keys. With cloning:

Your current keys usually stay valid, so you don't need a full new key set.
The rest of the car sees the same identity data it always has.
The process avoids adapting every related module from zero.

The catch is that cloning requires that the original switch's data can still be recovered. If the old switch is damaged so badly that its data can't be read, other approaches are needed, and the options depend on the car.

When You Need EIS Cloning

Cloning is typically the answer when:

The ignition switch has failed electronically or mechanically, but its data can still be read.
The switch is worn, the key sticks or won't turn, and you want to keep your current keys.
A steering lock problem has affected the switch. The EIS and ELV work as a pair, and on some cars both need attention. Mercedes' own bulletin for the Sprinter (906) steering lock problem called for an ignition switch replacement on some early vehicles along with the steering column.

If the steering lock is the root cause, see our Mercedes steering lock (ELV) failure guide.

A Note on Volkswagen Ignition Problems

Mercedes isn't the only European brand with ignition headaches. If you drive a VW, the owner's article Fixing Volkswagen ignition issues: the long-term solution covers that side.

What to Have Ready When You Call

Year, model and VIN
How many working keys you have
What happens when you insert and turn the key
Any warning lights or recent battery or electrical work

EIS Cloning With Eurokeys

Eurokeys offers EIS cloning for 1999 to 2013-14 Mercedes-Benz models, including the W204, W207, W212, GLK and Sprinter, along with steering lock replacement, key repair, making and duplication. See key fob programming and ELV steering lock replacement.

Having Ignition Switch Trouble? We Can Help

We're mobile, so we come to you in Richmond and the surrounding area. Call (804) 823-9268 and tell us your year, model, and what the switch is doing.