U14D800: Data Bus On Board Diagnostic Interface Control Module received malfunction value
Diagnostic trouble code U14D800 — what it means, the common
causes, and how to confirm the real fault before replacing parts.
What does U14D800 mean?
U14D800 indicates: Data Bus On Board Diagnostic Interface Control Module received malfunction value.
This relates to the Network / communication system.
Common causes of U14D800
Interruption of the fiber-optic cable causing a ring break on the MOST bus
Faulty voltage supply of the transmitter or receiver control module
Faulty transmitter or receiver control module on the MOST bus
Fatal errors detected in the affected control module causing it to disconnect from the bus (bus OFF) at least twice
Message time-out triggered when at least 10 messages are not received (delays in cyclic message traffic)
What to check (live data)
Gateway measuring value blocks (via VAS scan tool, Address Word 19 on later models, Address Word 17 on earlier models)
Ring break diagnosis via output diagnostic test mode of the diagnosis manager
Inspection plan retrieved from diagnostic tester via address code 005F (MOST150 bus ring break diagnosis)
FlexRay channel fault indication in diagnostic tester (channel A or B affected by short circuit)
Parts often involved in U14D800
Fiber-optic cable
Transmitter control module (MOST bus participant)
Receiver control module (MOST bus participant)
Data Bus On Board Diagnostic Interface J533
Optical replacement control unit VAS 6778
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 U14D800 — 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.
U14D800 is a diagnostic trouble code: Data Bus On Board Diagnostic Interface Control Module received malfunction value.
What are the common causes of U14D800?
Common causes include: Interruption of the fiber-optic cable causing a ring break on the MOST bus, Faulty voltage supply of the transmitter or receiver control module, Faulty transmitter or receiver control module on the MOST bus, Fatal errors detected in the affected control module causing it to disconnect from the bus (bus OFF) at least twice. The exact cause depends on the vehicle — confirm it before replacing parts.
Can I keep driving with U14D800?
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 U14D800?
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 U14D800 on your specific vehicle.