BMW bulletin B121126
What it saysPotential customer complaints with no fault codes stored / No MIL displayed. 1. “Rough idle after idling for a longer period of time” 2. “Vehicle feels like it is misfiring at idle” The automatic Start/Stop function… NHTSA’s full summary ↓
BMW filed this with NHTSA as a service bulletin dated Sep 9, 2026, received Sep 28, 2026, about the engine. It names 9 model years (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.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationPotential customer complaints with no fault codes stored / No MIL displayed. 1. “Rough idle after idling for a longer period of time” 2. “Vehicle feels like it is misfiring at idle” The automatic Start/Stop function is deactivated. The vehicle is stopped and the engine runs at idle speed. After prolonged idle operation (approximately 30 to 50 seconds), a slight jolt or slight change in idlespeed may be noticeable. There are no relevant errors in the DME fault code memory. No mixture control error, no misfiring, no error relating to a relevant component of the drive system. Motor vehicles affected: 1. Only MHEVs (mild hybrid electric vehicle) with crankshaft-driven starter generator. 2. Only vehicles with optional equipment 01CE = recuperation system 3. Affected I-levels: I-level 24-07-500 or higher
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| B121126 | Service bulletin | Sep 9, 2026 | 11037505 | PDF, 99 KB |
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 themA vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
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What owners reported
Source: NHTSA complaint databaseOwners of the 9 model years this bulletin names have filed 297 complaints with NHTSA since 2015. 17 of them name Engine — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
I am started to lease this car in August 2024. After 2 weeks, the car just halted, unable to move. Luckily this happened in my driveway. It took BMW more than 1 month to repair this. They had to change the combined charging unit with a different part number (upgraded part). At that time the car had roughly 200 miles on the odometer.
2024 BMW X5 · Engine · filed with NHTSA Apr 23, 2024
The contact owns a 2024 BMW X7. The contact stated that while driving 70 MPH, the vehicle stalled. There was an unknown message regarding the brakes, stability control, and steering displayed. There was a red symbol displayed. Additionally, while driving at an unknown speed or a stop light, the brakes locked up.
2024 BMW X7 · Engine · filed with NHTSA Oct 17, 2024
Vehicle was parked at approximately 3:45 PM. While parked, the vehicle engine caught fire sometime in the next hour, approximately. Many eyewitnesses stated that nobody was seen near the vehicle as it started smoking, and then caught fire, with multiple explosions heard.
2024 BMW 2 Series · Engine · filed with NHTSA Oct 20, 2024
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the engine
Source: same model, same component group78 other manufacturer communications filed against these BMW models under the same component group (engine), newest first. The eight newest are listed; the rest are on the BMW list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| 1171901000 | Warranty extension | Sep 22, 2026 | The Exhaust Gas Recirculation (EGR) Cooler (with EGR Valve) and the Auxiliary Exhaust Gas Recirculation (EGR) Cooler limited warranty for de… |
| 0011460700 | Emissions | Aug 26, 2026 | The return springs on the exhaust camshaft followers (switchable rocker arm) may break. |
| B064426 | Other | Aug 22, 2026 | Air Flap Return |
| B130126 | Service campaign | Aug 14, 2026 | Delivery Stop - Exhaust System Gasket |
| 0018030200 | Service campaign | Aug 14, 2026 | An exhaust gas sealing ring between thelower catalytic converter and upper catalyticconverter may be missing (1). |
| B110326 | Service bulletin | Aug 12, 2026 | This Service Bulletin provides instructions to clean the intake valves using the BMW Carbon Blaster Tool P/N 81 29 2 208 034 and the S68T /… |
| B064126 | Other | Aug 6, 2026 | Fan Return |
| 1613911200 | Warranty extension | Aug 3, 2026 | the NVLD modules limited warranty for defects in materials and/or workmanship has been extended to 15 years / 150,000 miles as determined fr… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for BMW, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is BMW B121126 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 B121126 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 B121126 cover?
The manufacturer filed it against 9 model years: 2024 BMW 2 Series, 2024 BMW 3 Series, 2024 BMW 4 Series, 2024 BMW 5 Series, 2024 BMW 7 Series, 2024 BMW X3 and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.