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Service bulletins for the 2021 Audi S4

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.

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

By type

By component

By trouble code

Only bulletins with component: Electrical system are shown. Show all

Bulletins, newest first
A9121312061028_32021-10-05. Service bulletin. ELECTRICAL SYSTEM; EQUIPMENT. This bulletin explains and troubleshoots when Audi connect does not have a green SOS light.
A9121162061257_22021-09-03. Service bulletin. ELECTRICAL SYSTEM:SOFTWARE. This bulletin contains instructions regarding Audi connect software failures and how to resolve it.
A9121142053916_32021-08-04. Service bulletin. ELECTRICAL SYSTEM:SOFTWARE; EQUIPMENT. This informational bulletin contains instructions for when a non-plus sized iPhone heats up while wirelessly charging and the CarPlay screen may appear frozen.
A9021092063913_12021-07-02. Service bulletin. EQUIPMENT; ELECTRICAL SYSTEM: INSTRUMENT CLUSTER/PANEL; ELECTRICAL SYSTEM:SOFTWARE. This bulletin contains a software update for when the cluster's driver information system is blank.
A9121092063702_12021-07-02. Service bulletin. ELECTRICAL SYSTEM; EQUIPMENT; EQUIPMENT ADAPTIVE/MOBILITY. This bulletin states to create a PSS when the MMI display turns blue. Workaround provided.
A9121082063290_12021-07-02. Service bulletin. EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL; ELECTRICAL SYSTEM. This bulletin contains instructions for troubleshooting FoD malfunctions.
A4821022061904_32021-07-02. Service bulletin. STEERING; EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL; ELECTRICAL SYSTEM. This bulletin contains repair instruction for when DTC C110DF0 is stored and the yellow steering lamp is on.
A9121052061933_22021-06-03. Service bulletin. ELECTRICAL SYSTEM: INSTRUMENT CLUSTER/PANEL; EQUIPMENT:ELECTRICAL:NAVIGATIONAL SYSTEM(GLOBAL POSITIONING SYSTEM). This bulletin contains an explanation and troubleshooting for the Navigation messages in the instrument cluster.
A9121042024323_82021-06-03. Service bulletin. EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL; ELECTRICAL SYSTEM:ADAS:PARKING ASSIST:SOFTWARE. This bulletin contains technical information regarding when the parking aid sporadically warns of obstacles that don't exist or it is inoperative/constant warning.
ELSAallignAudi2021-05-06. Service bulletin. ELECTRICAL SYSTEM. Elsa2Go campaign information is now 100% aligned with ElsaPro. This update to Elsa2Go ensures that both systems are displaying the same campaign information, including OPEN/CLOSED status, repair date as well as criterions at the same time without any discrepancy.
A9021982059335_22021-05-06. Service bulletin. ELECTRICAL SYSTEM: INSTRUMENT CLUSTER/PANEL; ELECTRICAL SYSTEM. This bulletin contains information on noises from the instrument cluster installation area.
A9021992063038_12021-05-06. Service bulletin. ELECTRICAL SYSTEM: INSTRUMENT CLUSTER/PANEL; ELECTRICAL SYSTEM. This informational bulletin explains why the version information pops-up.
A5721752022032_92021-05-06. Service bulletin. LATCHES/LOCKS/LINKAGES; ELECTRICAL SYSTEM. This technical service bulletin provides troubleshooting information for the vehicle locking system.
A9121822062115_32021-04-06. Service bulletin. ELECTRICAL SYSTEM. This bulletin contains instructions for when the nav files are corrupted during an update.
SM 17-20212021-04-06. Service bulletin. ELECTRICAL SYSTEM. This special notice is to inform dealers to return the parts listed if it meets the criteria provided.
A0121992054893_42021-04-06. Service bulletin. ELECTRICAL SYSTEM. This bulletin contains instructions for documenting the "Please reduce Oil Level" message in the instrument cluster potentially with an Engine Warmup request.
A9721782061976_12021-03-04. Service bulletin. ELECTRICAL SYSTEM. This bulletin contains guidance for submitting warranty wiring repairs.
A9121672061625_22021-03-04. Service bulletin. ELECTRICAL SYSTEM. This bulletin states to create a PSS record when the message "SOS - Emergency call malfunction, please contact service" is displayed in the instrument cluster and DTCs B129B11 and B239C11 are stored in the control module for emergency call module and communication unit.
A4821922061904_12021-02-04. Service bulletin. EQUIPMENT; EQUIPMENT ADAPTIVE/MOBILITY; ELECTRICAL SYSTEM. This bulletin contains repair instruction for when DTC C110DF0 is stored and the yellow steering lamp is on.
A5320042043016_22021-01-08. Service bulletin. ELECTRICAL SYSTEM:PROPULSION SYSTEM: CABLES; EQUIPMENT. This bulletin contains repair instructions for when cables are hanging in view with no DTCs.
A3920382060169_22021-01-08. Service bulletin. ELECTRICAL SYSTEM. This bulletin contains instructions for when DTC U101300 is logged with sports differential warning lamps or messages.
21A4S4ALRDCSDEL2021-01-08. Service bulletin. ELECTRICAL SYSTEM. Infotainment Section: ADDED: Check radio settings and ensure 'Online additional data' is toggled on and 'online station tracking' is set to Automatic
A9120362061345_12020-12-04. Service bulletin. ELECTRICAL SYSTEM; EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL. This informational bulletin contains information regarding connectivity issues.
A9120272061257_12020-12-04. Service bulletin. ELECTRICAL SYSTEM:SOFTWARE. This bulletin contains instructions regarding Audi connect software failures and how to resolve it.
21A4S4TECHREP2020-11-05. Service bulletin. EQUIPMENT; ELECTRICAL SYSTEM. Driver Assistance Section: ADDED: "Activate rear cross traffic assist (if equipped)"

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