FAQ
TL;DR: In one A6 C6 case, 6/6 modules reported optical errors; "Optical data bus diagnostics: Standard." Treat this as a ring break and inspect fiber links. [Elektroda, leonek4, post #17402897]
Why it matters: For Audi A6 C6 owners and techs chasing black screens and dead buttons, this FAQ streamlines optical-bus diagnosis and fixes.
Quick Facts
- Fault 00384 = Optical Databus Open Circuit in CAN Gateway; fix wiring/module causing the break. [Elektroda, leonek4, post #17405624]
- A full-ring failure example showed 6/6 modules with Optical ERROR in the initial scan. [Elektroda, leonek4, post #17402897]
- Sound-system amplifier (47) sits in the trunk and can drop communication. [Elektroda, leonek4, post #17405624]
- Isolate faults by bridging modules and checking for light at fiber ends. [Elektroda, fructon, post #17403559]
- Add +3 dB attenuation during optical-bus testing to aid diagnosis. [Elektroda, vwaudi, post #17696647]
Black MMI screen and dead buttons—what does a scan showing many Optical ERRORs mean?
It points to an optical ring break. In one case, all listed nodes showed Optical ERROR. Start by inspecting fiber links and connectors, then isolate modules on the ring. Power may be fine, but data light isn’t completing the loop. [Elektroda, leonek4, post #17402897]
How do I find the faulty module on the optical bus?
Bridge modules one by one and watch for light. How-To: 1. Unplug a module and insert an optical loop bridge. 2. Check if the far-end fiber glows red. 3. Reconnect modules sequentially until the ring collapses again; the last added module or its wiring is suspect. [Elektroda, fructon, post #17403559]
What does fault 00384 (Optical Databus Open Circuit) mean?
The CAN Gateway detected a break in the optical loop. The ring is incomplete or a module isn’t passing light. Inspect the affected segment, reseat connectors, and confirm power and ground at that module. Clear the fault and rescan after each change. [Elektroda, leonek4, post #17405624]
Which components are commonly water-damaged in the A6 C6?
Users report flooded radio and amplifier causing boot loops or shutdowns. If the MMI shows a logo then dies, re-check these trunk modules for corrosion. Clean, reflow, or replace as needed. “These elements are often flooded” in this model. [Elektroda, autotrek, post #19947145]
Where are 07, 0E, 56, 47, and 37 modules located?
From reports: 47 amplifier is in the trunk; 07 control head is by the gear shifter; 37 navigation sits in a storage compartment with status LEDs. Check trunk electronics and stowage areas for fiber plugs when tracing 0E Media Player 1 and 56 Radio. [Elektroda, leonek4, post #17405624]
How do I run an optical-bus test with attenuation?
Use your diagnostic tool’s optical-bus routine and add attenuation to stress the link. As one expert advised: “Make optical bus test with damping + 3dB.” This helps reveal marginal modules or poor connections during the light test. [Elektroda, vwaudi, post #17696647]
After a weak battery, my MMI 2G High died. Which nodes should I check first?
Target modules that show both electrical or optical errors. In a later scan, two nodes flagged first: 07 control head and 0E media player. Inspect their power, ground, and fiber connections, then rescan to confirm recovery. [Elektroda, radekstypka, post #21258123]
Speakers knock and MMI won’t start—where do I begin?
Start at the CAN Gateway. A permanent 00384 fault means the optical cable path is open. Check the radio and information electronics for communication. Isolate the ring with loop bridges and verify light at each step. Then clear codes and retest. [Elektroda, kubas10, post #19686916]
Nav unit LEDs flash alternately, but no communication—what’s happening?
The navigation drive has power, but it cannot talk on the optical ring. The ring is broken, or another module isn’t forwarding light. Verify the nav’s fiber connections and continue ring isolation until communication returns. [Elektroda, leonek4, post #17405624]
My scan shows 07-Control Head ERROR-ERROR. What does that imply?
Both electrical and optical paths report faults for the control head. Check the console panel harness, power, ground, and its fiber link. If the module stays offline, swap in a known-good unit to confirm. [Elektroda, radekstypka, post #21258123]
MMI shows the startup logo, then shuts off—what should I check?
Inspect trunk electronics for prior water damage, especially radio and amplifier. Clean or replace oxidized boards and reseat fiber connectors. A boot-then-die pattern suggests a module crashes the ring shortly after initialization. [Elektroda, autotrek, post #19947145]
I reseated the trunk amplifier and status changed, but it still fails. Next steps?
Confirm the presence of optical fibers at the trunk amplifier plug. If optics are missing at that connector, trace the harness backward. Keep bridging non-essential modules to keep the ring closed during testing. [Elektroda, kubas10, post #19687974]
I bridged everything and left only the radio, but MMI stays dark—why?
Radio-only tests can still fail. The gateway expects a closed optical loop, and the control head orchestrates wake-up. Use proper loop plugs across every removed node and rescan. Verify radio power, ground, and its fiber continuity. [Elektroda, JakubRybka, post #21573208]
How do I interpret Electrical OK but Optical ERROR entries?
Power and CAN reach the module, but optical communication fails. The fiber ring is open or a node isn’t relaying light. Focus on fiber continuity and bridging to restore the optical loop before replacing parts. [Elektroda, leonek4, post #17402897]
Where can I buy an optical loop bridge for testing?
Search for a “fiber-optic bridge/loop Audi.” These inexpensive loop plugs let you bypass a suspect node cleanly during testing. Insert them at each module to keep the ring closed while isolating faults. [Elektroda, fructon, post #19948039]
Is a single “MMI computer” to blame if nothing powers up?
The A6 C6 spreads MMI across several modules, so you won’t find a single box. If you can’t locate a single “MMI computer,” test the optical ring and each node in sequence to pinpoint the fault. [Elektroda, leonek4, post #17408808]
