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Why Won't the Key Turn in a Mercedes Ignition?

Model: Mercedes Mercedes Various
Part: Key

Video tutorial

The problem described in the video is a Mercedes that has suddenly locked up. The key won't turn in the ignition, and the dashboard won't light up. In this condition, it’s impossible to even connect a diagnostic tool to the OBD port to understand the fault by reading the errors on the control units.

The main suspicion for these vehicles is the ES, which is the electronics of the ignition lock; this control unit is integrated with the electromechanical steering lock.

If it fails, it prevents the key from turning. Specifically, for the vehicle in question, the problem was the SAM (Signal Acquisition Module), which manages much of the electrical system and fuses.

The one in this car was full of corrosion and irreparable, effectively preventing communication with the rest of the vehicle, including the starting system. The solution is complex: the YouTuber cloned a salvage SAM unit, which has different hardware and software from the original.

Now the car starts, but all control units will need to be coded to get the vehicle functioning properly again.


Posted on 19 September 2026 by ScegliAuto


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