This part is listed by BMW as BMW part number 12315A284D3 (12 31 5 A28 4D3) and is described as the voltage regulator or carbon brush set for the alternator used on B58C and B58D engines in G42 M240i, G20 M340i, G22/G26 M440i, G30 540i, G12 740i, G15 840i, G01 X3/X4 M40i, X5/X6/X7 40i, G29 Z4 M40i. It's also used in all A90/GR Supra 40i models.
Electrical and charging issues are not always a "bad alternator". The voltage regulator on your B58 engine is located on the back of the alternator and it regulates the output voltage. A bad voltage regulator can fail to charge the battery at a sufficient rate (slow drain) and it can also allow too much voltage to enter back into the rest of the electrical system where it may damage voltage-sensitive components. Rebuilt alternators will include a new, or tested and approved, voltage regulator. But if you believe the alternator is good, the regulator can be replaced on its own to avoid a bigger repair bill.
Voltage regulators often vary by alternator brand and output. This regulator does not fit with the 48V Mild Hybrid system. BMW lists this for 150A, 180A, and 250A alternators.
This is a Genuine BMW B58 voltage regulator with a two year warranty. Buying a Genuine part will usually be more expensive than an OEM or aftermarket brand but you are assured that it meets BMW's designs for fitment, performance, and longevity. It will also be the very latest design, incorporating any updates or revisions that an aftermarket brand typically will ignore.
For full BMW fitment information or for assistance from one of our BMW experts, we recommend calling us at 877-639-9648.
BMW Fitments:
2 Series
G42 / G43 (2022+) > 230i
G42 / G43 (2022+) > 230i xDrive
G42 / G43 (2022+) > M240i
G42 / G43 (2022+) > M240i xDrive
3 Series
G20 (2019+) > 330i
G20 (2019+) > 330i xDrive
G20 (2019+) > M340i
G20 (2019+) > M340i xDrive
4 Series
G22 / G23 (2021+) > 430i
G22 / G23 (2021+) > 430i xDrive
G22 / G23 (2021+) > M440i
G22 / G23 (2021+) > M440i xDrive
4 Series
G26 (2022+) > 430i Gran Coupe
G26 (2022+) > 430i xDrive Gran Coupe
G26 (2022+) > M440i xDrive Gran Coupe
5 Series
G30 (2017-2023) > 530i B46D (2020-2023)
G30 (2017-2023) > 530i xDrive B46D (2020-2023)
G30 (2017-2023) > 540i (B58C 2020-2023)
G30 (2017-2023) > 540i xDrive (B58C 2020-2023)
7 Series
G12 (2016-2023) > 740i
G12 (2016-2023) > 740i xDrive
X3 Series
G01 X3 (2018-2024) > X3 M40i B58D (2020-2024)
G01 X3 (2018-2024) > X3 sDrive30i (2020-2024)
G01 X3 (2018-2024) > X3 xDrive30i (2020-2024)
X4 Series
G02 X4 (2019-2024) > X4 M40i B58D (2020-2024)
G02 X4 (2019-2024) > X4 xDrive30i (2020-2025)
X5 Series
G05 X5 (2019+) > X5 sDrive40i RWD B58C (2019-2023)
G05 X5 (2019+) > X5 xDrive40i B58C (2019-2023)
X6 Series
G06 X6 (2020+) > X6 sDrive 40i B58C (2020-2023)
G06 X6 (2020+) > X6 xDrive 40i B58C (2020-2023)
X7 Series
G07 X7 (2019+) > X7 xDrive40i B58C (2019-2022)
Z Series
G29 Z4 (2019-2025) > Z4 M40i
G29 Z4 (2019-2025) > Z4 sDrive30i