What it does
The BDC carries the body functions, the access and immobilizer system, terminal control and gateway duties in one domain controller. It appeared first around 2013–2014 on the F15 X5 and F16 X6 and the i3 and i8, then on the front-drive family — the X1 (F48), X2 (F39) and the Mini F5x and F60 range — and it became the body module of the G-series, until the access and immobilizer functions of BMW's newest models moved to the Basic Computing Platform (BCP) from 2021 on.
The hardware inside has been revised several times: a G30 built before mid-2020 or a G01 built before mid-2021 does not take the same unit as a later one, and the X5 moved to the BCP with the 2023 facelift. A replacement has to match the production date, not just the model.
How it fails, and what gets replaced first by mistake
One fault still reads as a cluster of unrelated symptoms, as with the FRM and FEM before it. On 794 X1 and X2 built in June 2018, BMW's service action SI B61 07 19 replaced the BDC because cavity wax had dripped onto it and its connector in the passenger footwell. And because it holds the car's key and immobilizer data, replacement is a programming and data-transfer job, not a swap.
Generations this applies to
Jobs where this was the fault
From a documented source: BMW SI B61 07 19 (BDC); transpondery.com CAS/FEM/BDC list; MINI SIM 61 03 24 (BDC).
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