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Service bulletins for the 2021 Hyundai Sonata

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.

109 on file from NHTSA, as of 2026-10-19.

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Bulletins, newest first
26-EM-016H TSB2026-10-14. Service bulletin. ENGINE. Some vehicles equipped with internal combustion engines may exhibit higher-than-expected engine oil consumption. This bulletin outlines the combustion chamber cleaning procedure for vehicles diagnosed with this condition. All internal combustion engines consume some engine oil during normal operation, depending on driving conditions and mileage, and this procedure should only be performed when deemed necessary based on inspection and diagnosis of the vehicle as outlined in TSB 26-EM-015H, Engine Oil Consumption – Inspection & Repair Guidelines, or the latest revision.
26-EM-015H TSB2026-10-13. Service bulletin. ENGINE. Certain vehicles equipped with internal combustion engines may exhibit higher-than-expected engine oil consumption. This bulletin provides the inspection and repair procedures for vehicles exhibiting this condition. All internal combustion engines consume engine oil as part of normal engine operation. Oil consumption rates may vary based on mileage, operating conditions, driving habits, and maintenance history. Hyundai recommends following the prescribed maintenance schedule and periodically checking the engine oil level using the dipstick to maintain proper engine oil level.
26-AT-005H TSB2026-06-16. Service bulletin. POWER TRAIN. This bulletin provides information related to a Transmission Control Unit (TCU) software update for some vehicles equipped with an 8-speed wet dual clutch transmission (8WDCT). The software update revises the touch point learning variation, improving drivability and judder symptoms. Some 8WDCTs (indicated by a new part number) received an updated clutch spring. The correct TCU software update must be matched with the correct corresponding 8WDCT hardware, otherwise, drivability concerns may occur. This service procedure should be performed prior to any 8WDCT replacements done for drivability/judder concerns.
DTN DL2026-05-08. Other. AIR BAGS. The National Highway Traffic Safety Administration (NHTSA) has identified the presence of substandard and dangerous driver’s-side airbag inflators manufactured by Jilin Province Detiannuo Automobile Safety System Co., Ltd. (DTN). These inflators were not supplied, approved, or authorized by the vehicle manufacturers and have primarily been found in vehicles that previously experienced a crash and underwent airbag replacement using non-genuine parts. These dangerous inflators have ruptured during deployment, posing a serious risk of injury or death due to metal fragments entering the vehicle cabin. To date, Hyundai is aware of three people who have died while driving a Hyundai vehicle with one of these substandard replacement airbag inflators that deployed in what likely would have been a survivable crash. NHTSA has issued a public advisory urging vehicle owners and service professionals to have vehicles inspected if there is reason to believe that a non-genuine replacement airbag may have been installed. Vehicles with salvage or rebuilt titles, prior airbag deployments, or unknown repair histories may present a higher risk. NHTSA strongly cautions against self-inspection by vehicle owners and recommends inspection by trained technicians.
DTN DCS2026-05-08. Other. AIR BAGS. The National Highway Traffic Safety Administration (NHTSA) has issued an urgent safety advisory regarding dangerous, counterfeit driver‑side airbag inflators manufactured by Jilin Province Detiannuo Automobile Safety System Co., Ltd. (DTN), that have been identified in U.S. vehicles following prior crashes, theft, or non‑certified airbag replacements. These inflators are not approved for use, may rupture during deployment, and have caused serious injuries and fatalities. Please see attached announcement, provided by NHTSA, for more details.
26-EE-003H TSB2026-04-21. Service bulletin. ENGINE; ELECTRICAL SYSTEM. Some vehicles may exhibit difficulty starting in cold weather. This bulletin provides the procedure to perform an inspection on the starter magnetic switch for potential freezing and, if necessary, replace the starter magnetic switch (solenoid) assembly.
26-AT-001H TSB2026-03-11. Service bulletin. POWER TRAIN. Some Santa Cruz (NXT), Santa Fe (TMA, MX5A), and Sonata (DN8A) models may require replacement of the 8-speed wet dual clutch transmission (8WDCT) when the vehicle sets one of the high pressure electric oil pump (HP EOP) DTCs listed below. This bulletin provides instructions to replace the 8WDCT.
26-AD-001H TSB2026-03-07. Service bulletin. FORWARD COLLISION AVOIDANCE: WARNINGS; LANE DEPARTURE: ASSIST; EXTERIOR LIGHTING; FORWARD COLLISION AVOIDANCE: ADAPTIVE CRUISE CONTROL; LANE DEPARTURE: WARNING. Some 2019MY and newer vehicles equipped with a front view camera may illuminate certain warning lights and trigger DTC C272246 fault code for the front camera. In the following cases, the front camera auto-calibration range may be exceeded while driving: • If the front camera is not properly installed and is completely or partially detached. • In case of excessive changes affecting the vehicle's balance (e.g., loading excessively heavy cargo in a specific location of the vehicle, or significant under-inflation of the tires). • Specific road conditions affecting the vehicle's balance (e.g., excessive road crown) This TSB provides instructions on how to service the vehicle when the front camera related warning light(s) are triggered due to system out of calibration (DTC_C272246).
26-EM-003H TSB2026-02-10. Service bulletin. ENGINE. Some Sonata (DN8, DN8A) vehicles may have DTCs P218100, P2181F0, and/or P2181F1 (Cooling System Performance) set in the Engine Control Module, resulting in an illuminated Check Engine warning lamp. Follow the procedure in this TSB to replace the Integrated Thermal Management (ITM) module and update both the Engine Control Module (ECM) and Transmission Control Module (TCM) if applicable. Follow the flowchart in this TSB to update the appropriate modules.
26-FL-001H TSB2026-01-13. Service bulletin. FUEL/PROPULSION SYSTEM. Some vehicles equipped with a 2.5L GDI Theta III engine (non-Turbo) may exhibit one or more misfire DTCs due to the GDI fuel injectors leaking internally. This may be caused by internal filter breakage in the injector. Follow the procedure in this TSB to replace all 4 injectors on affected vehicles, using the kit in the Parts Information section.
25-EM-007H TSB2026-01-06. Service bulletin. ENGINE. Some Elantra (CN7, CN7A), Kona (OS, SX2), and Sonata Hybrid (DN8 HEV) vehicles equipped with 2.0L engines may illuminate a warning lamp for DTC P218100 (Cooling System Performance) related to the Integrated Thermal-Management Module (ITM). Follow the service procedure in this bulletin to install a spring onto the thermostat within the ITM, in order to prevent premature opening, and perform an ECU software update on affected vehicles.
25-BD-012H TSB2025-11-12. Service bulletin. EXTERIOR LIGHTING. This bulletin provides information regarding condensation related to the accumulated moisture in the headlamp, rear combination lamp, daytime running lamp (DRL), or fog lamp. This TSB illustrates the various causes of condensation inside the lamp assembly. Lamp assembly replacement is NOT necessary in most cases. This condition can be eliminated by turning on the lamps with the engine running for several minutes or during normal driving operation.
25-BE-020H TSB2025-10-03. Service bulletin. ELECTRICAL SYSTEM. This bulletin provides information related to the changes introduced in the 2025 1st Navigation Map and Software Update. The changes may vary depending on vehicle type, model, and navigation system as described in this TSB.
25-01-010H-1 9B4 OL2025-08-22. Service campaign. ELECTRICAL SYSTEM. Certain Hyundai vehicles may exhibit a warning light with Diagnostic Trouble Code (“DTC”) P1BB20 due to a battery over voltage condition.
25-01-010H-1 DN2025-07-22. Service campaign. ELECTRICAL SYSTEM. Certain Elantra Hybrid (CN7 HEV), Sonata Hybrid (DN8 HEV), and Tucson Hybrid (NX4 HEV) vehicles may exhibit a warning light due to DTC Code P1BB20 (12V Lithium Battery Cell Voltage High). The California Air Resources Board has determined that these vehicles may be releasing air pollutants which exceed Federal and California standards.
25-01-010H-1 TSB2025-07-22. Service campaign. ELECTRICAL SYSTEM. This bulletin provides the procedure to update the software for the Battery Management System (BMS) on certain Elantra Hybrid (CN7 HEV), Sonata Hybrid (DN8 HEV), and Tucson Hybrid (NX4 HEV) vehicles that may exhibit a warning light with DTC P1BB200 and enter Limp Mode.
25-AT-001H TSB2025-06-03. Service bulletin. POWER TRAIN. Certain Santa Fe (TMA) and Sonata (DN8/DN8A) vehicles equipped with 8-speed dual clutch transmissions (8DCT) may exhibit one of the DTCs listed below, related to the high pressure electric oil pump (HP EOP). Follow the procedures in this TSB to update the Transmission Control Unit (TCU) to the latest sensorless logic on affected vehicles, and then perform air bleeding and transmission learning.
25-BE-002H TSB2025-06-03. Service bulletin. ELECTRICAL SYSTEM. This bulletin provides information related to the changes introduced in the 2024 2nd Navigation Map and Software Update. The changes may vary depending on vehicle type, model, and navigation system. Refer to the 2024 2nd Navigation Map and Software Update Improvements section in this TSB for a list of specific changes. The software can be downloaded via Navigation Updater (NAU) and updated by USB. The NAU website is https://update.hyundai.com/US/EN/navigationUpdate. For certain models equipped with a relevant Bluelink package, the software may be downloaded and applied via OTA update.
25-01-024H-1 TSB2025-05-27. Service campaign. ELECTRICAL SYSTEM. Some vehicles may exhibit a loss of connectivity or interruptions in the middle of using Bluelink Service functions. This may be due to an irregular disconnection on Verizon’s communication network. Follow the procedure in this TSB to reestablish the connection via the AVN pinhole reset method.
25-EE-002H2025-05-02. Service bulletin. ENGINE; ELECTRICAL SYSTEM. Certain Sonata (DN8) and Sonata (DN8A) vehicles may experience issues with the air conditioning due to damaged wiring in the engine room junction box. This bulletin provides instructions to replace the multi-fuse, reroute the damaged wiring using the blower wiring kit, and replace the fuse label.
25-EE-002H TSB2025-04-30. Service bulletin. ELECTRICAL SYSTEM. Certain Sonata (DN8) and Sonata (DN8A) vehicles may experience issues with the air conditioning due to damaged wiring in the engine room junction box. This bulletin provides instructions to replace the multi-fuse, reroute the damaged wiring using the blower wiring kit, and replace the fuse label.
25-01-024H EM2025-04-18. Service campaign. ELECTRICAL SYSTEM. Some vehicles may exhibit a loss of connectivity or interruptions in the middle of using Bluelink Service functions. This may be due to an irregular disconnection on Verizon's communication network. If you are experiencing issues with remote commands, or other Bluelink services, please see the instructions below to reestablish the connection via the AVN pinhole reset method.
25-01-024H TSB2025-03-25. Service campaign. ELECTRICAL SYSTEM. Some vehicles may exhibit a loss of connectivity or interruptions in the middle of using Bluelink Service functions. This may be due to an irregular disconnection on Verizon’s communication network. Follow the procedure in this TSB to reestablish the connection via the AVN pinhole reset method.
25-01-010H DN2025-02-17. Service bulletin. FUEL/PROPULSION SYSTEM. Certain Elantra hybrid (CN7 HEV), Sonata hybrid (DN8 HEV), and Tucson hybrid (NX4 HEV) vehicles may exhibit a warning light due to DTC Code P1BB20 (12V Lithium Battery Cell Voltage High). Follow the procedure in TSB 25-01-010H (or latest version) to perform the update the Battery management System (BMS) software.
25-01-010H TSB2025-02-17. Service campaign. FUEL/PROPULSION SYSTEM. This bulletin provides the procedure to update the software for the Battery Management System (BMS) on certain Elantra Hybrid (CN7 HEV), Sonata Hybrid (DN8 HEV), and Tucson Hybrid (NX4 HEV) vehicles that may exhibit a warning light with DTC P1BB20.

The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.