There is very little in the way of diagnostics for the speaker and amplifier.
Ista D would tell you if the car can communicate with the Head unit and the
Most Bus modules. If you have the Logic 7 system there are diagnostic LED's
on the Logic 7 amp .
If the Head unit is dead (no power) there is fuse on the back of the head unit as well as the fuse in the Cabin fuse board.
If you hope to do this your self you will have to know which Head Unit you have and which
Sound system you have .
So basically you have to know something about the system to fix it, unless you get lucky.
Frm modules are noted to be fragile and often die with just programming it is not
common for the modules in the rest of the system to fail that easily .
Any BMW shop should have something that reads an programs the modules.
You can get ista d and standard tools that does this on laptop for the cost of
a K/D can cable (bimmergeeks.com ) and free downloads you can find online.
Though it's not as easy to get as it used to be and there is some setup and a learning
curve . Or you could get Bimmergeeks Pro tool for your phone.
Doesn't mean that you won't have to do homework to understand the system.
diagnostic manual ista/inpa
https://www.google.com/url?sa=t&rct=...xo19teM9vkTF-C
https://www.google.com/url?sa=t&rct=...7x8H3pN8h1fMuF
https://bimmerprofs.com/diagnostics-inpa-part-1/
https://www.google.com/url?sa=t&rct=...lkXEhlQYy4i9Nb
https://www.bimmerforums.com/forum/s...-P-actually-do
https://www.bimmerfest.com/forums/at...1&d=1590283589
https://www.google.com/url?sa=t&rct=...kBbC27TJLX3BGe
https://www.google.com/url?sa=t&rct=...WekqhcC6hsgK2c
primary links
https://www.e90post.com/forums/showthread.php?t=1681573
https://www.nathansbmwworkshop.com/b...or-dean-videos
ista problems
https://www.e90post.com/forums/showthread.php?t=1661945
https://www.e90post.com/forums/showthread.php?t=1581663
https://www.bimmerfest.com/threads/t...-pdfs.1449540/