U0100 on Audi
Lost Communication with ECM/PCM
U0100 on Audi vehicles indicates lost communication with ecm/pcm. Au7o has documented this code across 3 Audi models — most commonly on A6, Q5 Sportback, S7. 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.
Common Causes of U0100
- •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
U0100 on Audi by Model
Audi A6(1 issue)
- Gateway Control Module Liquid-Ingress Recall 90V2 (22V-861)2019-2022
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.
Audi Q5 Sportback(1 issue)
- 2021-2022 Audi Q5 Sportback Gateway Recall 90S9 / NHTSA 21V9472021-2022
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.
Audi S7(1 issue)
- Rear-Seat Liquid Spill Can Shut Down Gateway Module (Recall 22V861 / 90V2)2020-2022
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.
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View U0100 across all makes →Frequently Asked Questions
What does U0100 mean on 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 specifically, this code is documented across 3 models.
What causes U0100 on Audi vehicles?▼
Common causes on Audi: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix U0100 on a Audi?▼
Repair costs vary widely depending on the root cause and specific Audi model.
Which Audi models have U0100 documented?▼
Au7o has documented U0100 on 3 Audi models: A6, Q5 Sportback, S7.