FAQ
TL;DR: 12,000 PLN new MMI, 1.5–3k PLN used; "Watch out for batteries." If your Audi A6 C7 MMI boots then dies after a flat battery, replace the head unit and adapt Component Protection to restore functions. [Elektroda, malygt, post #17100671]
Why it matters: For Audi A6 C7 owners asking "how do I fix MMI after battery died?", this gives a proven path and real costs.
Quick Facts
- Symptom: screen appears for a few seconds, then goes blank; MMI won’t start. [Elektroda, malygt, post #17082852]
- Scan result: “no communication” with radio/media points toward the center-console MMI unit. [Elektroda, malygt, post #17084011]
- Costs: new head unit ~12,000 PLN; used ~1,500–3,000 PLN; labor ~1,700 PLN. [Elektroda, malygt, post #17100671]
- Diagnosis: ODIS bus-attenuation test identifies the failing MOST component. [Elektroda, Anonymous, post #17088823]
- After replacement: remove Component Protection and load software/maps to restore features. [Elektroda, malygt, post #17100671]
Why did my Audi A6 C7 MMI stop working after the battery died?
Deep discharge and voltage drop can damage the main MMI head unit. In the reported case, the module failed and required replacement. The fix included installing a used head unit, removing Component Protection, and loading software/maps. Protect the car from extended low-voltage periods to avoid repeat failures. [Elektroda, malygt, post #17100671]
What are the classic symptoms of this MMI failure?
The screen powers on briefly, then shuts off. The MMI doesn’t fully boot, and functions remain unavailable. Owners often describe it as the display appearing for seconds and disappearing. These symptoms point to a non-responsive head unit on the MOST ring. [Elektroda, malygt, post #17082852]
My scan shows "no communication" with radio/media—what does that indicate?
Loss of communication across several infotainment modules suggests the head unit in the center console is offline. Technicians then focus on the MMI main module located near the SD/CD area. Schedule deeper diagnostics to confirm the failing node. [Elektroda, malygt, post #17084011]
Can ODIS pinpoint the failed MOST component?
Yes. ODIS can run a bus attenuation test to identify the faulty device on the optical ring. As one tech put it: "ODIS can perform a bus attenuation test" and flag the damaged component. This streamlines isolation and repair decisions. [Elektroda, Anonymous, post #17088823]
How do I isolate a bad module with an optical loop?
Use an optical loop to bypass devices one at a time on the MOST ring.
- Insert the loop in place of one device, restoring the ring.
- Start at the left trunk amplifier and test MMI boot.
- Move forward device-by-device until the MMI boots, identifying the bad node. [Elektroda, malygt, post #17082852]
Is Component Protection stopping my MMI?
Component Protection can lock functions after module swaps. A proper scan should show CP-related errors at address 07 when available. As one expert noted, "Most likely component protection has been activated." You’ll need CP removal via authorized tools. [Elektroda, domex32, post #17083108]
I can’t find address 07—what should I do?
Some vehicles won’t show address 07 in user-level scans. Continue diagnosis using full vehicle diagnostics and MOST testing rather than relying on a single address. Don’t assume modules are fine because 07 is missing in your scan list. [Elektroda, malygt, post #17083581]
What actually fixed the issue in this thread?
Replacing the MMI with a used unit resolved the no-boot problem. After installation and required setup, the system returned to normal operation. This confirms head-unit failure as the root cause in this case. [Elektroda, malygt, post #17135100]
How much should I budget for parts and labor?
Expect about 12,000 PLN for a new head unit from the dealer. Used units typically cost 1,500–3,000 PLN. Labor was reported around 1,700 PLN for installation, CP removal, software, and maps. That’s a realistic 3,200–14,700 PLN total. [Elektroda, malygt, post #17100671]
Where is the A6 C7 MMI head unit located?
Technicians identify the main MMI module in the center console area. It sits near the SD card and CD reader slots. When scans show multiple infotainment modules offline, inspect this central unit first. [Elektroda, malygt, post #17084011]
Will a weak battery really kill the MMI, or is that a myth?
Owners and techs report weak or dead batteries often precede MMI failure. One member summarized it as "Quite a common fault." Avoid extended parking without charging and replace aging batteries proactively to protect electronics. [Elektroda, Anonymous, post #17101391]
I bridged the amplifier and MMI still won’t start—what next?
If bypassing the amplifier doesn’t restore boot, suspect the head unit. Run an ODIS bus attenuation test to confirm the failing MOST node. As noted by a tech, the "MMI headset has actually fallen" in many such cases. [Elektroda, Anonymous, post #17088823]
After replacing the head unit, what setup is required?
Complete Component Protection removal, then load the correct software and latest navigation maps. This brings back full features and clears CP restrictions. The reported repair followed this sequence with successful operation afterward. Keep the vehicle on a stable power supply during updates. [Elektroda, malygt, post #17100671]
