2008 A8 MMI don't work
 

Any idea how to get this working? The MMI on the 2008 A8 stopped working after the radio radio made a crackling noise. It suddenly stopped working for a while in the past and an electrician replaced the tuner in the trunk. It worked for 3 weeks and now dead again. It boots and initialize then goes black and cause a clock ticking sound coming from the rear passenger side speaker area. Any ideas?

You need a VCDS scan, but sounds like a break in the MOST bus fibre optic ring is a possibility or a fatal fault in one of the devices on the ring (which will break the ring)

Thanks! Whats the most reasonable VCDS scan tool out there? Can the tool isolate the cables or just send me in a rat nest?