B58 Gen 3: why your 2023-on M340i can't be tuned yet

BMW quietly changed control units mid-generation. If your M340i is a facelift car, this is why nobody can tune it.

If you have a facelift M340i, a current 540i or a recent X5 40i and every tuner you have asked has said no, you are not being fobbed off. The Gen 3 B58 sits on a control unit nobody has an unlock for, and that has been true since it arrived.

What changed

Earlier B58s ran a Bosch MG1 control unit, which is well understood and routinely unlocked. Around 2023, alongside the 48V mild-hybrid system, BMW moved the engine onto a newer unit — the DME9 generation. Nobody currently has a working unlock for the Gen 3 B58 on it. That is the whole explanation, and it applies to every tuner, not just us.

The luxury models switched before the M Performance ones. A 540i or an X7 40i is more likely to be Gen 3 than an M340i of the same model year, which is exactly the sort of thing that catches people out.

Which cars are affected

How to tell which one you have

Roughly: a 2023-or-later facelift car with the 48V mild-hybrid setup is probably Gen 3. A pre-facelift M340i from 2019 to 2022 is Gen 2 and perfectly tunable once unlocked. But the changeover was not clean, it varied by model, and it varied by market.

Do not guess on this one, and be careful with the chassis code — the same G20 designation covers both. The VIN is the only thing that settles it, and checking costs nothing.

If someone says they can do it

Ask a lot of questions. Ask which control unit they think is in your car. Ask what happens to your money if it fails. This is an area where the honest answer loses the sale, which is precisely why you should be suspicious of anyone giving you a different one.

Will it ever be possible?

Probably. This has happened before — every generation of locked DME has eventually been opened, and the tooling moves faster than most people expect. The S68 V8 sits on the same DME9 unit and can now be unlocked, which is the clearest sign the tooling is moving.

Send us the VIN and we will tell you plainly where your car sits today. If coverage arrives for it later, we will let you know rather than leaving you to find out.

What you can still do in the meantime

Tuning is off the table on these cars. Coding is not, and the two are unrelated — the lock that stops your DME being flashed has nothing to do with the modules that run your lighting, your chimes and your comfort features.

So on a Gen 3 B58 we can still change how the car behaves: ambient and interior lighting, the seatbelt reminder and the warnings that nag, and features your car already supports but left switched off. It adds no power and it is not a substitute for a tune. It is just the part of the car that is still open to you.