U1121 on Audi
Databus - Missing Message
U1121 on Audi vehicles indicates databus - missing message. Au7o has documented this code across 10 Audi models — most commonly on A8, e-tron, Q8. The control module expected a specific message on the data bus and it never arrived within the required time window. Like U1111 this is a downstream complaint - the module reporting it is fine, but a peer module or the bus itself stopped delivering data. Audi TSB 2061788 lists U112100 ("Databus missing message") among the codes stored in high-voltage battery charger J1050 on 2020-2021 e-tron, where the cause was outdated onboard-charger software; on SQ5/SQ8 air-suspension complaints (Audi TSB 2059363) it points at the air-suspension controller J1135 dropping off the bus.
Common Causes of U1121
- •Transmitting control module offline, failed, unpowered, or not coded
- •Outdated module software producing spurious bus timeouts (documented on Audi e-tron OBC software 0070)
- •CAN wiring damage, corroded connector, or poor ground
- •Gateway J533 installation list not matching the vehicle's actual modules
- •Low battery voltage or a discharged battery causing modules to drop off
- •Aftermarket electrical accessory loading or disturbing the bus
U1121 on Audi by Model
Audi A8(1 issue)
- 2019-2025 A8 Air-Suspension Warning C1260F0/U112100 - TSB 2059363/62019-2025
On air-suspension-equipped 2019-2025 Audi A8 vehicles, the cluster may show an air-suspension malfunction warning while the suspension controller stores C1260F0 or U112100 with symptom code 262400. Audi directs diagnosis toward communication, wiring and connector contacts between the suspension controller and compressor control module; the bulletin does not establish that every warning is a failed compressor, leaking spring or collapsed suspension.
Audi e-tron(2 issues)
- 2019-2023 e-tron Air-Suspension Warning with J1135 Communication Fault - Diagnosis Required2019-2023
Audi TSB 2059363/5 covers a legacy e-tron air-suspension malfunction when suspension controller J775 stores C1260F0 for no communication with compressor-control unit J1135 or U112100 with symptom code 262400 for a missing message. This is an electrical communication path; the bulletin does not establish leaking air lines, worn struts, height-sensor failure, compressor burnout or ball-joint wear as one common defect.
- 2021 e-tron Charging Interruptions with Onboard-Charger Software 0070 - Diagnosis Required2021
Audi TSB 2061788/2 covers model-year 2021 e-tron quattro and e-tron Sportback vehicles with specified AC/DC charging interruptions, charging-flap operation problems, or an app request for auxiliary heating that does not pre-heat the vehicle when matching DTCs are stored in high-voltage battery charger control module J1050. Audi attributes the documented condition to onboard-charger software and identifies old software level 0070, not a proven failed charger module.
Audi Q8(1 issue)
- 2019-2025 Q8 Air-Suspension J1135 Communication Fault - TSB 2059363/62019-2025
Audi TSB 2059363/6 applies to air-suspension-equipped 2019-2025 Q8 vehicles when the instrument cluster reports an air-suspension malfunction and suspension control unit J775 stores C1260F0 for no communication or U112100 for a missing message, both with symptom code 262400. The bulletin identifies communication with compressor-control unit J1135; it does not establish universal air-spring, strut or compressor wear.
Audi RS Q8(1 issue)
- 2020-2025 RS Q8 Air-Suspension J1135 Communication Fault - TSB 2059363/62020-2025
Audi TSB 2059363/6 applies to air-suspension-equipped 2020-2025 RS Q8 vehicles when the instrument cluster reports an air-suspension malfunction and suspension control unit J775 stores C1260F0 for no communication or U112100 for a missing message, both with symptom code 262400. The bulletin identifies communication with compressor-control unit J1135; it does not establish universal air-strut, air-spring, compressor or complete-system wear.
Audi RS6(1 issue)
- 2021-2024 RS6 Air-Suspension Warning - Check C1260F0 or U1121002021-2024
Audi TSB 2059363/5 covers an air-suspension malfunction warning on 2021-2024 RS6 Avant vehicles when the suspension controller stores C1260F0 or U112100 with symptom code 262400. The bulletin is about communication with the compressor-control module, not proof that an air strut leaks or that the compressor has been overworked.
Audi RS7(1 issue)
- 2021-2025 RS7 Air-Suspension J1135 Communication Fault - TSB 2059363/62021-2025
Audi TSB 2059363/6 applies to air-suspension-equipped 2021-2025 RS7 vehicles when the instrument cluster reports an air-suspension malfunction and suspension control unit J775 stores C1260F0 (no communication) or U112100 (missing message), both with symptom code 262400. The bulletin identifies communication between J775 and compressor-control unit J1135; it does not establish a universal air-strut, compressor or complete-system wear failure.
Audi S8(1 issue)
- 2020-2024 S8 Air-Suspension Malfunction with J1135 Communication Fault - Diagnosis Required2020-2024
Audi TSB 2059363/4 covers an air-suspension malfunction on 2020-2024 S8 vehicles when the suspension controller stores C1260F0 for no communication with the compressor control unit or U112100 with symptom code 262400 for a missing message. The bulletin identifies the electrical path between level-control module J775 and compressor-control unit J1135, not a general leaking-strut or worn-compressor population.
Audi SQ5(1 issue)
- Air-Suspension Warning with C1260F0 or U112100 Communication Fault2018-2025
On SQ5 vehicles equipped with air suspension, Audi documents an air-suspension warning accompanied by C1260F0 or U112100 with symptom code 262400 in suspension control module J775. The bulletin concerns communication with compressor control module J1135; it does not support the former blanket claims about leaking air springs, failed dampers, vehicle sag or weight-related wear.
Audi SQ7(1 issue)
- 2020-2025 SQ7 Air-Suspension C1260F0/U112100 Communication Fault - Diagnosis Required2020-2025
On 2020-2025 SQ7 vehicles equipped with air suspension, Audi documents an air-suspension warning accompanied by C1260F0 or U112100 with symptom code 262400 in suspension control module J775. The bulletin concerns communication with compressor control module J1135 and states that improved J1135 software is under development as the production solution; it does not promise an owner-installed update or replace the bulletin diagnostic branches. The bulletin does not support the former blanket claims about leaking air struts, compressor overwork, vehicle weight, sagging, nose dive or rough ride.
Audi SQ8(1 issue)
- 2020-2025 SQ8 Air-Suspension J1135 Communication Fault - TSB 2059363/62020-2025
Audi TSB 2059363/6 applies to air-suspension-equipped 2020-2025 SQ8 vehicles when the instrument cluster reports an air-suspension malfunction and suspension control unit J775 stores C1260F0 for no communication or U112100 for a missing message, both with symptom code 262400. The bulletin identifies communication with compressor-control unit J1135; it does not establish universal air-strut, air-spring, compressor or complete-system wear.
Looking for U1121 on a different make?
View U1121 across all makes →Frequently Asked Questions
What does U1121 mean on Audi?▼
U1121 stands for "Databus - Missing Message." The control module expected a specific message on the data bus and it never arrived within the required time window. Like U1111 this is a downstream complaint - the module reporting it is fine, but a peer module or the bus itself stopped delivering data. Audi TSB 2061788 lists U112100 ("Databus missing message") among the codes stored in high-voltage battery charger J1050 on 2020-2021 e-tron, where the cause was outdated onboard-charger software; on SQ5/SQ8 air-suspension complaints (Audi TSB 2059363) it points at the air-suspension controller J1135 dropping off the bus. On Audi specifically, this code is documented across 10 models.
What causes U1121 on Audi vehicles?▼
Common causes on Audi: Transmitting control module offline, failed, unpowered, or not coded, Outdated module software producing spurious bus timeouts (documented on Audi e-tron OBC software 0070), CAN wiring damage, corroded connector, or poor ground, Gateway J533 installation list not matching the vehicle's actual modules, Low battery voltage or a discharged battery causing modules to drop off. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix U1121 on a Audi?▼
Repair costs vary widely depending on the root cause and specific Audi model.
Which Audi models have U1121 documented?▼
Au7o has documented U1121 on 10 Audi models: A8, e-tron, Q8, RS Q8, RS6, RS7, S8, SQ5, SQ7, SQ8.