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Service bulletin B340521

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id10194297
Published by NHTSA2021-05-24
Manufacturer's numberB340521
Manufacturer's date2021-04-01
NHTSA componentEQUIPMENT; SERVICE BRAKES, AIR:DISC; EQUIPMENT ADAPTIVE/MOBILITY

NHTSA's summary

Diagnosis of Compound Brake System Complaints in M Vehicles: 1. Visible cracks are caused by high thermal stresses during rapid heating and cooling of the brake discs. Braking from high speed with cold brake components (less than 212 degrees F) increases the likelihood of cracks to form.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Brakes, Equipment and accessories

Vehicles listed
BMW 840I2020, 2021
BMW M82020, 2021
BMW M8 GRAN COUPE2020
BMW M850I2019
BMW M850I2020, 2021
BMW M850XI2019

Listing a model year does not mean every vehicle of it is concerned: the document says which.

Recalls for the same vehicles and component
21V0620002021-02-10. SERVICE BRAKES, HYDRAULIC:POWER ASSIST:HYDRAULIC; SERVICE BRAKES, HYDRAULIC

A recall listed here may apply to some of the same vehicles. Only the manufacturer can say whether it applies to one vehicle.

Other bulletins for the same vehicles and component
B6607202024-03-02. Service bulletin. The functionality of the left rear SRR sensor could be reduced which would display the Driving Assistance Check Control Message.
B6608202024-03-02. Service bulletin. The functionality of the right rear SRR sensor could be reduced which would display the "Driving Assistance"- Check Control Message.
B6105242024-02-01. Service bulletin. The Central Information Display goes black intermittently due to resets of the Head Unit (HU-H3). FaultB7F8F9 â“ âHU-H: Resetâ will be stored in the HU-H3.
B3407142023-11-01. Service bulletin. Functional noises (squealing/honking) when braking shortly before the vehicle comes to a stop. CAUSE Material-
B8403232023-07-24. Service bulletin. BMW AG has issued a Delivery Stop (effective February 9, 2023) on certain Model Year 2022 - 2023 BMW vehicles that were produced between June 29, 2022 and February 16, 2023.
B1203232023-07-24. Service bulletin. BMW AG has issued a Delivery Stop effective June 6, 2023 on certain Model Year 2023 - 2024 BMW vehicles that were produced between October 26, 2022 and May 8, 2023.
B8403232023-06-26. Service bulletin. BMW AG has issued a Delivery Stop (effective February 9, 2023) on certain Model Year 2022 - 2023 BMW vehicles that were produced between June 29, 2022 and February 16, 2023. This was originally called ""Wireless Charging Tray"". Software in potentially affected vehicles may not recognize the removal of the digital key (Key Card or mobile phone) from the wireless charging tray, and thereby not meeting a federal requirement."
B8414222023-05-01. Service bulletin. Customer is shown an incorrect GPS location in the vehicle (i.e., Nav Map, coordinates).
B8408222023-05-01. Service bulletin. The 3G network in the US has been shut down. This means that only the 4G network will be available. In the 4G network, voice calls will be transferred via the Voice over LTE (VoLTE) function. For this purpose, the SIM card must perform an IMS registration in the mobile communication network. Due to a production error, the telematics control units were delivered without an IMS configuration. The Connected Drive voice services (Concierge Call, BMW Assistance, and emergency call voice) can no longer be used regionally in the US in vehicle with telematics control units ATM-1 and TCB-4G. Voice control of the vehicle and all other telephone (paired mobile devices) functions are not affected. Emergency call location data is unaffected.
B6516232023-05-01. Service bulletin. Customer states there is no audio playback (telephony, navigation, radio) and system sounds (PDC, turn indicators, acoustic signals) may also have failed.