BMW bulletin B120721
BMW filed this with NHTSA as a service bulletin dated Mar 4, 2024, received Dec 6, 2023, about the engine and engine cooling — 2 documents under this number. It names 50 model years (2017–2024). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationCheck Control message (CCM) indicates: (ID 213): Stop, exercising due care. Voltage supply The Service Engine Soon light is on with the following DME Fault Code: 21B209 - Starter alternator / belt for 48V system (OSA_RIEMEN_RISS): Belt betweenCombustion engine and starter generator torn And/or one or more of the following other issues are also occurring: Noise in the area of the belt drive. Odor from the engine compartment. Smoke formation in the area of the belt drive. Drive belt damaged or prematurely worn. Torn drive belt.
Documents filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| B120721 | Service bulletin | Mar 4, 2024 | 10252038 | not yet checked |
| B120721 | Service bulletin | Nov 9, 2023 | 10245367 | not yet checked |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themAlso filed against model years this site has no page for: 2020 BMW 330E; 2020 BMW 340I; 2023 BMW 340I; 2017 BMW 530E; 2019 BMW 540D; 2020 BMW 540D; 2022 BMW 540D; 2023 BMW 540D; 2020 BMW 550E; 2021 BMW 550E; 2020 BMW 640I.
A vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
Common questions
Source: NHTSA, 49 CFR 579.5Is BMW B120721 a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the B120721 repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way.
Which vehicles does B120721 cover?
The manufacturer filed it against 50 model years: 2024 BMW 3 Series, 2023 BMW 3 Series, 2022 BMW 3 Series, 2021 BMW 3 Series, 2020 BMW 3 Series, 2019 BMW 3 Series and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.