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
| A9421342012749_1 | 2021-03-04. Service bulletin. EXTERIOR LIGHTING. This bulletin contains instructions for addressing condensation in the headlights. |
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| A9121692062115_2 | 2021-03-04. Service bulletin. EQUIPMENT. This bulletin contains instructions for when the nav files are corrupted during an update. |
| A9121682062266_1 | 2021-03-04. Service bulletin. EQUIPMENT:ELECTRICAL:NAVIGATIONAL SYSTEM(GLOBAL POSITIONING SYSTEM). This bulletin states to create a PSS record when last destinations, favorites, and home/work addresses are sporadically lost. |
| A9121672061625_2 | 2021-03-04. 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. |
| A4621222051095_4 | 2021-03-04. Service bulletin. EQUIPMENT. This informational bulletin contains instructions on how to download and use the Audi Frequency App. |
| A9421332061922_1 | 2021-03-04. Service bulletin. EQUIPMENT. This informational contains instruction on how to document optical concerns for warranty claims. |
| A462124203418118 | 2021-03-04. Service bulletin. SERVICE BRAKES. This technical service bulletin provides troubleshooting for brake noise. |
| A462123202258410 | 2021-03-04. Service bulletin. SERVICE BRAKES. This informational bulletin provides diagnostic information for brake conditions. |
| A4421802056386_4 | 2021-03-04. Service bulletin. STEERING. This bulletin contains instructions for when the vehicle pulls to one side or the steering wheel is crooked. |
| A6621692030471_6 | 2021-03-04. Service bulletin. EQUIPMENT. This informational bulletin covers the condition of when license plate mounting bracket threaded inserts are stripped. |
| A4421792022563_1 | 2021-03-04. Service bulletin. WHEELS. This bulletin provides information regarding vibrations or movement that are felt in the wheel. |
| A1721122060750_2 | 2021-03-04. Service bulletin. ENGINE AND ENGINE COOLING. This bulletin contains instructions for using the UV additive to find engine oil leaks. |
| SM 05-2021 | 2021-02-04. Service bulletin. EQUIPMENT. This special notice is to inform dealers to return the parts listed if it meets the criteria provided. |
| A9121642024323_7 | 2021-02-04. Service bulletin. PARKING BRAKE:ELECTRICAL:CONTROL MODULE. This bulletin contains technical information regarding when the parking aid sporadically warns of obstacles that don't exist or it is inoperative/constant warning. |
| A9121622061934_1 | 2021-02-04. Service bulletin. EQUIPMENT. This bulletin states to ignore DTCs U156C00, B1A06F1, B1A06F2 and to not perform any repairs or run any test plans for these ghost DTCs. |
| A1921112061918_1 | 2021-02-04. Service bulletin. ENGINE AND ENGINE COOLING. This bulletin provides guidance on diagnosing a coolant light concern with normal coolant level in the tank. |
| A6621682046229_2 | 2021-02-04. Service bulletin. STRUCTURE. This informational bulletin outlines proper warranty procedure for optical defects. |
| A4821922061904_1 | 2021-02-04. 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. |
| A0121962060429_2 | 2021-02-04. Service bulletin. ENGINE AND ENGINE COOLING; EQUIPMENT; EQUIPMENT ADAPTIVE/MOBILITY. This bulletin contains instructions for when there may be a noise from the exhaust flap or there are DTCs sporadically stored in the ECM. |
| A9120432061625_1 | 2021-01-08. Service bulletin. EQUIPMENT ADAPTIVE/MOBILITY; EQUIPMENT:ELECTRICAL. SOS emergency call malfunction, DTC B129B11 and B129C11 are stored in the emergency call control module |
| A5320042043016_2 | 2021-01-08. Service bulletin. ELECTRICAL SYSTEM:PROPULSION SYSTEM: CABLES; EQUIPMENT. This bulletin contains repair instructions for when cables are hanging in view with no DTCs. |
| A5520512014055_8 | 2021-01-08. Service bulletin. EQUIPMENT; ENGINE; EQUIPMENT ADAPTIVE/MOBILITY. This bulletin contains instructions for addressing discoloration due to moisture on a new vehicle. |
| A3920382060169_2 | 2021-01-08. Service bulletin. ELECTRICAL SYSTEM. This bulletin contains instructions for when DTC U101300 is logged with sports differential warning lamps or messages. |
| 21A4S4ALRDCSDEL | 2021-01-08. 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 |
| SM C-2020 | 2021-01-08. Service bulletin. EQUIPMENT. This special notice is to inform dealers to return the part numbers listed (State of California only). |
The summaries are NHTSA's. Each bulletin's page links NHTSA's copy of the manufacturer's document.