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Since 1993, when early versions of DAS were introduced, all Mercedes vehicles have used DAS to validate the key as part of the ignition process enabling your car to start. If there’s an issue with the DAS it could be a reason why your car key isn’t working.

Prior to this, DAS was separate to the engine control module (ECM) and the ignition worked solely on a mechanical basis.

mercedes das

What is DAS?

DAS is an electronic system used by Mercedes which validates the car key and in so doing allows the car key to start.

Every Mercedes key fob using DAS has an infrared chip containing a fixed serial number and a rolling code. Every time you turn the key in the ignition, both the code and the serial number are read by DAS. This data is transferred to the electronic ignition switch (EIS) which allows the key to turn.

As the DAS element in keys is infrared and gets its power from an inductive coil in the ignition switch, there’s no need for battery power in the key to start the car, whereas your remote central locking system does require battery power.

How does the rolling code system work?

The rolling code system means that the code stored on your key is compared with a bank of codes stored in DAS. If a match is found, the engine control module (ECM) allows the engine to start, and a new code will be written onto the key. The next time the key’s used, it must supply this new code

Problems arise if your key fails to be validated. You might be able to turn it in the ignition, but even if it can physically turn, the ECM won’t allow the engine to start if the key isn’t recognised as valid.




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