U0100 on Audi: How to Diagnose & Fix
Lost Communication with ECM/PCM
3 Audi models · 3 documented issues · 3 critical
U0100 on Audi by model: symptoms, diagnosis and fix
NHTSA campaign 21V947 / Audi 90S9 covers certain 2021-2022 Q5 Sportback vehicles. A rear-seat liquid spill or water entry through an insufficient underbody seam can reach the gateway-control module and cause it to shut down, suddenly reducing engine power. This is not a universal mild-hybrid battery or start/stop failure. Eligibility is VIN-specific.
Common Symptoms
- Multiple control-system warnings
- Sudden reduction in engine power
How to Fix
Check the VIN and campaign-completion history with Audi or NHTSA. The free remedy installs a protective gateway-module cover and seals the underbody seam when necessary. If multiple warnings appear or engine power drops, move out of traffic safely and arrange dealer inspection; do not order a 12-volt battery from this card.
Sources for this issue (1)
Certain 2019-2022 Audi A6 Sedan and 2020-2022 A6 allroad vehicles are included in safety recall 22V-861, Audi campaign 90V2. Liquid spilled on the rear seat can reach the gateway control module beneath the rear middle seat. If the module detects implausible signals or internal short circuits, its safety strategy can shut down gateway communication. Multiple warnings can appear and engine power can be reduced unexpectedly. Audi states that the engine remains running in emergency mode and that steering and braking remain available; the earlier claim that this recall causes complete engine shutdown was inaccurate.
Common Symptoms
- Multiple warning messages appear after liquid is spilled on the rear seat
- Engine power is reduced and the vehicle enters emergency mode
- Gateway communication faults affect several vehicle systems
How to Fix
Check the VIN in Audi's official recall lookup and have an authorized Audi dealer complete campaign 90V2 if it is open. The recall remedy is installation of a protective cover over the gateway control module at no charge. Do not buy a scanner, repair manual, or replacement gateway module as the recall fix. If warning messages or sudden reduced power occur, move out of traffic safely and arrange prompt dealer diagnosis; a module already affected by liquid requires vehicle-specific diagnosis and campaign or warranty handling.
Find a Audi dealer
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Open Audi dealer map in Google Maps ↗Call to confirm they service Audi vehicles and check your VIN, recall eligibility, parts availability, and appointment options.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
Check your VIN for an open recall before buying.A dealer repairs an open manufacturer recall at no charge. Confirm coverage with NHTSA first.- Gateway control module protective-cover recall remedy$0
An authorized Audi dealer verifies campaign 90V2 by VIN and installs the protective cover free of charge.
Owner tips & cautions
- TipEnter the VIN in Audi's campaign lookup; model and year alone cannot confirm whether 90V2 is open on a particular A6.
- WarningMultiple warnings and sudden reduced engine power require prompt dealer diagnosis. A generic OBD scanner or replacement module is not the recall remedy.
Sources for this issue (3)
On certain 2020-2022 S7 vehicles, liquid spilled in the rear seat can reach the gateway control module, shut it down, and suddenly reduce engine power.
Common Symptoms
- Multiple warning messages
- Sudden reduction in engine power
- Faults after a rear-seat liquid spill
How to Fix
Check the VIN and campaign history. Audi dealers install a protective gateway-module cover free of charge under campaign 90V2. If multiple warnings or reduced power occur after a spill, move out of traffic safely and arrange dealer inspection.
Sources for this issue (1)
U0100 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U0100 mean on a Audi?
U0100 stands for "Lost Communication with ECM/PCM." U0100 is a network communication code meaning a module has lost communication with the engine control module / powertrain control module (ECM/PCM) over the vehicle's data bus. The ECM/PCM is the brain that runs the engine, so when other modules can no longer 'talk' to it, the effects can be serious — a no-start, stalling, multiple warning lights, and many other modules logging faults at once. This is almost always a wiring, connector, power/ground, or bus fault, or a failure of the ECM/PCM itself, rather than a single sensor. It should be diagnosed promptly because the vehicle may be undrivable. On Audi it is documented across 3 models: Q5 Sportback, A6, S7.
What are the most common causes of U0100?
The most common causes of U0100 are: Loss of power or ground to the ECM/PCM, CAN bus wiring damage, short, or open circuit, Corroded, loose, or damaged connectors at the module, Blown fuse feeding the ECM/PCM, Failed ECM/PCM, Another faulty module pulling down the data bus, Water intrusion or corrosion in a connector/harness. The specific cause varies by vehicle.
How much does it cost to fix U0100 on a Audi?
Repair costs vary widely with the root cause and Audi model; each issue on this page carries its own estimate where one is published.
Looking for U0100 on a different make?
View U0100 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.