Help! M5 Audio doesn't work

[ILoveMPower]

Well, the battery died on the M, so we had to enter the ole "CODE." After entering this the controls work fine, but no matter what the volume is set to the most you can hear is some EXTREMELY subtle whistling coming from the speakers

any ideas on what this could be?

[BMWDriver]

What I see on your sig pic is that you might have another head unit handy. Try that in.

My comment's not much help I think, but I don't figure there's any other way; electronics tend to do so many weird things at times, often it's trial and error.

[attack eagle]

amp fuse?

[BMWDriver]

amp fuse?
Hey, that makes more sense !