Hi guys.

I havent used my radio for a while cause I had no speakers in the car. I recently installed a new hifi system (speakers, amp) and when I tried to test it I found that I no longer can turn on my radio/cd-changer/tape.

I can push the left knob on my 16:9 monitor but nothing happens. No orange light. Only thing that works is navigation (of course without sound) and boardcomputer.

So i used my OBD equipment - trying to figure out whats wrong:

-OBD talks to 16:9 monitor
-OBD talks to MK4 navigation
-OBD talks to cd-changer
-OBD does not talk to radio
-16:9 monitor fault code says "radio status telegramm timeout"

So - it appears that my radio cant communicate anymore. Two things are possible. Either the BM54 is simply dead - or I have damaged the wiring during hifi-installation (though I cannot imagine that I did).

How do I find out?

I did use the multimeter to check some wires. I know that the BM54 gets:

-permanent 12 Volt
-ignition 12 Volt
-grounding
-10A fuse is OK

I didnt know how to check the K-line - any ideas? What else besides the K-line would the BM54 need to communicate with either monitor or OBD? Does it need a bus-line to the MK4?

Please help. BM54 are hard to come by these days and are $$$. I need to know if the BM54 is really dead.

Any suggestions are welcome. Thanks!