Mercedes Benz

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Auto Locksmiths Ltd provides a complete mobile service for Mercedes‑Benz vehicles up to 2014, offering expert key cutting, programming and non‑destructive entry carried out directly at your vehicle. For models after 2014, a dealer key is required, and we are currently awaiting the release of the equipment needed to offer this service in the future.

Spare Mercedes Keys

If you need an additional Mercedes key, Auto Locksmiths Ltd can supply and program spare keys for vehicles up to 2014. Using specialist equipment, we read the vehicle’s data, extract the required security information and program a new key into one of the eight key slots allocated to the vehicle by the manufacturer. Your new key is cut and programmed while you wait.

Mercedes Lost Keys

If you’ve lost all your Mercedes keys, we can create and program a brand‑new key without replacing the ECU, ignition barrel or locks. Lost‑key situations require additional work because the information normally stored in the working key is unavailable. We retrieve the necessary security data from the vehicle and program a new key into one of the eight available slots.

General Mercedes Key Problems

If your Mercedes key won’t turn, the ignition doesn’t respond or you hear a juddering noise from the Electronic Steering Lock (ESL), Auto Locksmiths Ltd can help. We can test your key, the Electronic Ignition Switch (EIS) and the ESL to identify the fault.

The Mercedes EIS system uses a coded fob inserted into a dashboard socket. When inserted, the vehicle performs a series of security checks between the EIS, ESL and ECU. Only when all three modules confirm the key is authorised will the vehicle allow the “Turn & Start” function.

Mercedes Models Using the EIS System

The EIS module is fitted to almost all Mercedes models across the following chassis ranges:

W164, W168, W169, W202, W203, W204

W208, W209, W210, W211, W212, W215

W219, W220, W221, W230, W639, W906

Common Mercedes EIS / EZS Immobiliser Problems

• Key doesn’t turn in the EIS

• ESL does not release when the key is inserted

• Key turns but ignition lights do not come on

• Intermittent key turning issues

• Faulty or incorrect programming by previous garages

EIS Unit Faults

If the EIS unit becomes faulty, the vehicle will disable the “Turn & Start” function for security. This is a common issue and can be caused by:

• Jump‑starting the vehicle with the key inserted

• Power surges

• Low battery voltage

These issues can corrupt the EIS memory. The Mercedes STAR system cannot repair or re‑flash a failed EIS, and many failures are linked to the Motorola CPU chip inside the module, which is known to fail even in newer units.

The EIS stores vital key data and communicates with the ECU and ESL, meaning faults can appear as issues in other systems. Many EIS units can be repaired or replaced with service‑exchange units. If repair is not possible, we can supply a replacement in most cases.