U170B00: Control module for emergency call module and communication unit No communication on Ethernet data bus (Unauthorized)
Diagnostic trouble code U170B00 — what it means, the common
causes, and how to confirm the real fault before replacing parts.
What does U170B00 mean?
U170B00 indicates: Control module for emergency call module and communication unit No communication on Ethernet data bus (Unauthorized).
This relates to the Network / communication system.
Common causes of U170B00
Communication partner (J949) not responding on Ethernet data bus
Voltage supply fault to the Ethernet communication partner
Ethernet cable fault (open circuit, damage, or shielding issue)
What to check (live data)
Voltage supply to J949
Ethernet cable continuity/integrity check
Ethernet bus communication status via J533 event memory (Ethernet data bus branch no communication)
Parts often involved in U170B00
Ethernet cable (shielded or unshielded, 0.13 mm² copper-magnesium alloy strands)
Emergency call module control unit and communication unit J949
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 U170B00 — 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.
U170B00 is a diagnostic trouble code: Control module for emergency call module and communication unit No communication on Ethernet data bus (Unauthorized).
What are the common causes of U170B00?
Common causes include: Communication partner (J949) not responding on Ethernet data bus, Voltage supply fault to the Ethernet communication partner, Ethernet cable fault (open circuit, damage, or shielding issue). The exact cause depends on the vehicle — confirm it before replacing parts.
Can I keep driving with U170B00?
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 U170B00?
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 U170B00 on your specific vehicle.