U122C00 on Seat: Ethernet databus branch 1 no communication (Unauthorized)
Diagnostic trouble code U122C00 on Seat vehicles — what it means, the common
causes, and how to confirm the real fault before replacing parts.
What does U122C00 mean?
U122C00 indicates: Ethernet databus branch 1 no communication (Unauthorized).
This relates to the Network / communication system.
Common causes of U122C00
Communication partner not responding on Ethernet data bus branch
Faulty voltage supply to the communication partner control unit
Faulty or damaged Ethernet cable
What to check (live data)
Voltage supply to the communication partner control unit
Parts often involved in U122C00
Ethernet cable (shielded or unshielded twisted single pair)
Communication partner control unit on the affected branch
Don't replace parts until the root cause is confirmed — many of these codes are caused by wiring, a connector or an upstream fault, not the part itself.
Get the confirmed root cause for U122C00 — on YOUR vehicle
A code is a symptom, not a diagnosis. AutoDX Pro cross-checks several
independent assessments, pinpoints the actual root cause, gives you the
exact tests to confirm it, and shows the parts — only after the cause is
confirmed. Reads your scan-tool photo and decodes your VIN with open
recalls.
U122C00 is a diagnostic trouble code: Ethernet databus branch 1 no communication (Unauthorized).
What are the common causes of U122C00 on a Seat?
Common causes include: Communication partner not responding on Ethernet data bus branch, Faulty voltage supply to the communication partner control unit, Faulty or damaged Ethernet cable. The exact cause depends on the vehicle — confirm it before replacing parts.
Can I keep driving a Seat with U122C00?
It depends on the fault and your symptoms. Some causes are minor, others can damage components or affect safety. Get the root cause confirmed before deciding.
How do I fix U122C00 on a Seat?
Confirm the actual root cause with targeted tests first, then replace only the part that's at fault. AutoDX Pro gives you the root cause, the exact tests, and the parts for U122C00 on your specific Seat.