Locked ECUs from 2020: what MG1 and MD1 actually mean

Anyone driving a car built from roughly 2020 onwards and asking about chiptuning often gets a surprising answer: nothing goes through the diagnostic port any more. The reason is called MG1 or MD1 — the current generation of Bosch engine control units.

What changed

Earlier control units could be read and written through the OBD connector. On MG1 (petrol) and MD1 (diesel), write access is cryptographically secured. The memory area holding the maps is signed; without a valid signature the unit refuses to accept it.

This is neither accidental nor spite. Manufacturers are responding to regulatory requirements on tamper resistance for emissions and safety systems.

Which cars are affected

The switch did not happen on a single date but model by model, roughly between 2018 and 2021. Affected are newer BMW and MINI ranges, Mercedes-Benz from certain engine generations, and large parts of the VAG group. Whether your specific car belongs to them is only settled by reading it out.

The bench route

Where OBD access is blocked, direct access to the control unit remains. It is removed from the car and addressed on the bench through its internal interfaces. That takes more effort, more time and specialised hardware.

• Remove the control unit — 30 to 90 minutes depending on the car
• Read the original state via the bench interface
• Editing and checksum correction
• Write back and refit
• Adaptation and function test

What this means for coding

An important distinction: the lock concerns the engine control unit. Comfort coding on the head unit, instrument cluster and body control units is unaffected and still works normally through the diagnostic port — including remotely.

Being honest about it

On some cars the effort simply is not worth it. When removing the control unit costs more than the gain is worth, we say so. We would rather turn work down than leave a customer unhappy.