U112100 on Volkswagen: Data bus missing message (Unauthorized)
Diagnostic trouble code U112100 on Volkswagen vehicles — what it means, the common
causes, and how to confirm the real fault before replacing parts.
What does U112100 mean?
U112100 indicates: Data bus missing message (Unauthorized).
This relates to the Network / communication system.
Common causes of U112100
Missing messages from an affected control module (message time-out triggered when at least 10 messages are not received)
Control module disconnected from the bus (bus OFF) at least twice, storing a malfunction in DTC memory
Fatal errors detected in the affected control module causing it to be switched OFF by the CAN-bus
Short circuit between CAN-high and CAN-low
Short circuit between CAN-high and positive voltage
Short circuit between CAN-high and Ground
Short circuit between CAN-low and Ground
Short circuit between CAN-low and positive voltage
Open circuit in CAN-high data path
Open circuit in CAN-low data path
Diagnostic firewall blocking unauthorized access to sensitive vehicle data (active after vehicle has covered more than 200 km)
What to check (live data)
Gateway measuring value blocks (data blocks 125, 126) — active state of control modules connected to CAN-bus (1 = active, 0 = passive)
CAN-high wire voltage (Channel A on DSO)
CAN-low wire voltage (Channel B on DSO)
Drivetrain CAN continuity using ohmmeter
Convenience/Infotainment CAN signal using VAS 5051 DSO function
Parts often involved in U112100
CAN-bus wiring (CAN-high and CAN-low wires)
Affected control module(s) on the data bus
Data bus diagnostic interface J533 (Gateway)
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 U112100 — 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.
U112100 is a diagnostic trouble code: Data bus missing message (Unauthorized).
What are the common causes of U112100 on a Volkswagen?
Common causes include: Missing messages from an affected control module (message time-out triggered when at least 10 messages are not received), Control module disconnected from the bus (bus OFF) at least twice, storing a malfunction in DTC memory, Fatal errors detected in the affected control module causing it to be switched OFF by the CAN-bus, Short circuit between CAN-high and CAN-low. The exact cause depends on the vehicle — confirm it before replacing parts.
Can I keep driving a Volkswagen with U112100?
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 U112100 on a Volkswagen?
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 U112100 on your specific Volkswagen.