The 2021 M340i with the B58 engine is generally solid, but this generation saw ZF 8HP transmission cooler failures and isolated catastrophic engine failures tied to low-speed pre-ignition (LSPI). Most examples run well past 100k miles, but when things go wrong, they go expensive.
ZF 8HP Transmission Oil Cooler Failure
Common · high severity
Typical onset: 30,000-70,000 mi
Symptoms: Transmission fluid mixing with coolant (strawberry milkshake in expansion tank), Transmission slipping or harsh shifts, Check engine light with trans temp codes, Coolant loss with no visible leaks
Fix: Replace integrated transmission oil cooler inside radiator assembly, flush both coolant and transmission systems completely. 6-8 hours labor. If contamination sat long, trans may need rebuild or replacement (add 12-18 hours).
Estimated cost: $1,800-3,500 (cooler only); $6,000-9,000 if trans damaged
B58 Low-Speed Pre-Ignition (LSPI) Engine Failure
Rare · high severity
Symptoms: Sudden catastrophic loss of power, Loud knocking or rattling from engine bay, Metal debris in oil during change, Check engine light with misfire codes across multiple cylinders
Fix: LSPI causes piston ring land fracture and rod bearing failure. Requires complete short block replacement or engine rebuild with all pistons, rings, bearings, and often crankshaft. 25-35 hours labor. Affected engines often under 50k miles. BMW has issued updated piston rings for rebuilds.
Estimated cost: $12,000-18,000
Transmission Mount Failure
Occasional · low severity
Typical onset: 60,000-90,000 mi
Symptoms: Clunk when shifting from Park to Drive or Reverse, Vibration during acceleration, Excessive drivetrain movement visible from engine bay
Fix: Replace rubber transmission mount. Common wear item on higher-torque B58. 1.5-2.5 hours labor depending on access.
Estimated cost: $400-700
High-Pressure Fuel Pump (HPFP) Failure
Occasional · medium severity
Typical onset: 40,000-80,000 mi
Symptoms: Long crank or no-start condition, Rough idle and hesitation under load, Fuel pressure fault codes (29E7, 2A21), Limp mode activation
Fix: Replace high-pressure fuel pump on engine. B58 uses updated version vs older N55, but still fails. 3-4 hours labor including fuel system depressurization.
Estimated cost: $1,200-1,800
Valve Cover / PCV System Oil Leaks
Occasional · low severity
Typical onset: 50,000-90,000 mi
Symptoms: Oil smell in cabin or burning oil smell from engine bay, Visible oil on valve cover or upper engine, Oil consumption between changes (1 qt per 3,000 mi)
Fix: Replace valve cover gasket and PCV diaphragm (integrated into cover on B58). 4-5 hours labor. Common BMW issue across inline-6 platforms.
Estimated cost: $800-1,400
Rear Camera Failure (Recall 21V-846)
Occasional · low severity
Symptoms: Backup camera display shows black screen or distorted image, Camera image freezes intermittently, Water intrusion visible in camera housing
Fix: Camera housing seal allows moisture ingress. BMW recall covers replacement with updated sealed unit. 1 hour labor if not covered under recall.
Estimated cost: $0 (recall) or $500-800
Charge Pipe (Boost Pipe) Failure
Occasional · medium severity
Typical onset: 40,000-70,000 mi
Symptoms: Sudden loss of boost pressure, Loud hissing noise from engine bay under acceleration, Limp mode with underboost codes, Visible crack in plastic charge pipe near turbo outlet
Fix: Factory plastic charge pipe cracks at stress points. Aftermarket aluminum replacement recommended over OEM. 2-3 hours labor.
Estimated cost: $600-1,000
Owner tips
Use only BMW LL-01FE or LL-17FE+ spec oils and change every 5,000 miles to minimize LSPI risk—factory 10k interval is too long for aggressive driving
Check transmission fluid color at every service; pink or milky = immediate cooler replacement before trans damage
Avoid sustained low-RPM high-load situations (lugging in high gear) which trigger LSPI events
Budget $1,500/year for non-wear maintenance after warranty expires
Buy a 2021+ with full service records and transmission fluid documented clean; avoid 2019-2020 early B58 builds with higher LSPI rates—overall excellent platform if you can weather the occasional expensive repair.
AI-assisted summary drawn from NHTSA recall data, our labor-times database, and platform knowledge. Not a substitute for a pre-purchase inspection on a specific vehicle.
Fitment notes: AGM required; battery located in trunk; battery registration required after replacement
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Control Modules — 2021 BMW M340i
Every control module on the 2019-2021 BMW M340i — where it lives, replacement time, and what it takes to program a replacement. Modules marked dealer / factory tool won't work after a part swap alone — budget for programming.
⚠️ Fuel pressure relief required before service; basic adaptation sufficient
Aftermarket tool coverage varies by software version and vehicle build — treat "aftermarket tool" rows as "usually possible" and verify against your tool maker's coverage list before promising a customer. Spot a wrong location or hour? Tell us — corrections ship fast here.
BMW of North America, LLC (BMW) is recalling certain 2019-2022 330i, 330i xDrive, M340i, 2022 430i Coupe, 2021-2022 430i, M440i Convertible, and 2020-2022 228i xDrive Gran Coupe vehicles. The receiver audio module control unit software may fail to properly generate audible seat belt warnings to the driver to fasten their seat belt. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 208, "Occupant Crash Protection."
Consequence: An audible chime that does not properly alert the driver to fasten their seat belt increases the risk of injury in a crash.
Remedy: Dealers will update the receiver audio module software, free of charge. Owner notification letters were mailed October 12, 2023. Owners may contact BMW customer service at 1-800-525-7417.
SEATS · 23V211000
2023-03-29
BMW of North America, LLC (BMW) is recalling certain 2019-2021 330i, 330i xDrive, M340i xDrive, 2020-2021 X3 sDrive30i, X3 xDrive30i, X3 M40i, X3M, 2021 X3 xDrive30e, X4 xDrive30i, and X4M vehicles. The seat frame may not have been welded properly to the seat rails.
Consequence: An improperly welded seat frame may not properly restrain the occupant during a crash, increasing the risk of injury.
Remedy: Dealers will replace the seat frame and back rest, free of charge. Owner notification letters were mailed May 22, 2023. Owners may contact BMW customer service at 1-800-525-7417.
SEAT BELTS · 21V554000
2021-07-21
BMW of North America, LLC (BMW) is recalling certain 2021 2 Series (230i, 230i xDrive, M240i, M240i xDrive), 330e, 330e Xdrive, 4 Series Coupe (430i, 430i xDrive, M440i xDrive) M4 Coupe, M4 Competition Coupe, BMW 4 Series Convertible (430i, M440i), BMW X1 sDrive28i, xDrive28i, 2 Series Gran Coupe (228i, 228i xDrive, M235i xDrive), M2 Competition Coupe, 330i, 330i xDrive, M340i, M340i xDrive, M3, M3 Competition, 530i, 530i xDrive, 540i, 540i xDrive, MINI Hardtop 2 Door (Cooper, CooperS, JCW), X2 sDrive28i, X2 xDrive28i, X2 M35i, Z4 sDrive30i, Z4 M40i, MINI Hardtop 2 Door (Cooper SE), MINI Convertible (Cooper, Cooper S, JCW), MINI Clubman (Cooper S, Cooper S All4, JCW), MINI Countryman (Cooper, Cooper All4, Cooper S, Cooper S All4, JCW All4), Rolls Royce Ghost, MINI Countryman (Cooper S E All4), Rolls Royce Phantom, Rolls Royce Cullinan, and Toyota Supra vehicles. The passenger seat belt Automatic Locking Retractor (ALR) may deactivate early, before the webbing fully retracts. As such, these assemblies fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 208, "Occupant Crash Protection."
Consequence: During a crash, a seat belt retractor that does not function as intended increases the risk of injury.
Remedy: Dealers will inspect the seat belt retractors (including the seat belts) and, if necessary, replace the retractors, free of charge. Owner notification letters were mailed on September 3, 2021. Owners may contact BMW customer service at 1-800-525-7417; 1-866-825-1525 (MINI); 1-877-877-3735 (Rolls Royce); and 1-888-270-9371 (Toyota).
SEAT BELTS:FRONT:BUCKLE ASSEMBLY · 21V298000
2021-04-28
BMW of North America, LLC (BMW) is recalling certain 2021 330i, 330i xDrive, M340i, M3, and 330e xDrive vehicles. The bolt securing the seat belt assembly to the frame was not tightened to specification.
Consequence: An improperly installed seat belt assembly may not restrain an occupant as expected, increasing the risk of injury.
Remedy: BMW will notify owners, and dealers will inspect the front seat belt buckle assembly connection and, if necessary, replace it, free of charge. Owner notification letters were mailed on June 25, 2021. Owners may contact BMW customer service at 1-800-525-7417.
BACK OVER PREVENTION: SENSING SYSTEM: CAMERA · 21V096000
2021-02-19
BMW of North America, LLC (BMW) is recalling certain 2019-2021 X3 sDrive30i, X3 xDrive30i, X3 M40i, X3M, X4 xDrive30i, X4 M40i, M550i, X4M, X5 sDrive40i, X5 xDrive40i, X5 xDrive50i, X5M, X5 M50i, X7 xDrive40i, X7 xDrive50i, X7 M50i, Alpina XB7, 330i, 330i xDrive, M340i, M340i xDrive, and 8 Series Coupe, Convertible and Grand Coupe, 840i, 840i xDrive, M850i xDrive, M8, 2020-2021 530e, 530e xDrive, 330e, 330e xDrive, 745Le, 745Le xDrive, X5 xDrive45e, X3 xDrive30e, X6 sDrive40i, X6 xDrive40i, X6 xDrive50i, X6 M50i, X6M, 530i, 530i xDrive, 540i, 540i xDrive, M550i xDrive, M5, 740i, 740Li, 740Li xDrive, M760i Drive, M760Li xDrive, 750Li xDrive Alpina, Alpina B7 xDrive, and 2021 4 Series Coupe 430i, 430i xDrive, M440i xDrive vehicles.
When shifting into Reverse, a small portion of the rearview image may be obscured, or the screen may not illuminate. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard (FMVSS) number 111, "Rear Visibility."
Consequence: If the driver relies on only the rearview camera image, the missing or reduced rearview image view can increase the risk of a crash or injury.
Remedy: BMW will notify owners, and dealers will inspect the rearview camera software and update it if necessary, free of charge. The recall began April 16, 2021. Owners may contact BMW customer service at 1-800-525-7417.
ELECTRICAL SYSTEM:12V/24V/48V BATTERY · 20V761000
2020-12-09
BMW of North America, LLC (BMW) is recalling certain 2021 M340i xDrive, M440i xDrive Coupe, 530i, 530i xDrive, 540i, 540i xDrive, 740Li, 740Li xDrive, 840i Gran Coupe, 840i xDrive Gran Coupe, X5 sDrive40i, X5 xDrive40i, X6 sDrive40i, X6 xDrive40i, and X7 xDrive40i vehicles. The connection between the 48-Volt battery and the starter-generator may not have been assembled properly, which can cause increased electrical resistance at the connections.
Consequence: Increased electrical resistance can increase the risk of a fire.
Remedy: BMW will notify owners, and dealers will inspect the connection between the 48-Volt battery and the starter-generator assembly, replacing it if necessary, free of charge. The recall is expected to begin April 12, 2021. Owners may contact BMW customer service at 1-800-525-7417.
Size-standard part numbers — verify your connector type before buying. Rear blades are model-specific; check the package's vehicle list.
Fuel economy figures are EPA data via fueleconomy.gov (median across matching trims). Performance figures are compiled estimates for the 2021 BMW M340i 3.0L I6 Turbo B58 and can vary by trim.
🔧 Built by master technician Chris Hackleman · Master Technician · 20+ years.