1998 E38 radio has no sound but only has display - DSP unit has no display either

[thumpin1]

I have a 1998 740il non-vanos model. The radio head unit turns on but there is no sound - only display. No sound from radio unit, CD, or tape mode. The DSP unit has no display and doesn't work either. I can select channels and everything from the head unit. But there is just no sound coming from the speakers. Has anyone ran across this problem? I searched the forum but haven't found a problem with this specific issue.

[TheAngryBear]

Sounds like your dsp amp has gone. If you have a known hood one swap to see if it returns.


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[thumpin1]

Thanks. I have two old amps so I will try that and let you know.

[thumpin1]

Ok I pulled an amp out of another running 1998 740iL. The radio worked in the other car with flying colors so I know that amp worked great.
1. I put that amp in my 740iL and there was the same problem. Everything worked except for no sound and no display on the DSP. I could change channels on the radio, CD worked, and tape deck worked. Just no sound from the speakers.
2. I put my 'problem' amp from my car into the other 740iL. It worked great. Great sound, DSP worked, no problem.
3. At this point, I know MY original amp is good. So I put both amps back into their original cars.
I will try something else tomorrow (don't know what).

[thumpin1]

Ok I wanted to try disconnecting the battery for a couple hours this morning. But before that I went to the store and intentionally left the radio on - no sound but just the radio display showing. All of a sudden the radio just came on by itself while I was driving. I didn't touch anything. Just riding along and it startled me a bit to just hear the radio come on itself. So I started playing with the buttons, volume, modes, etc..... I even tried the CD and tape deck. ALL WORKED. I reluctantly turned the radio off just to see if it would come back on and it did. I got home with the radio playing enough and turned my car off. I didn't turn off the radio when I shut the car off. I turned the ignition back on and the radio display only came on with no sound and DSP not working - same a the problem before. I did this a few times with no luck. I started the car and still no luck. Tomorrow, I think I will disconnect the battery terminals and short the cables for a bit and reconnect the cables to the battery. I am just hoping to reset things.

[TheAngryBear]

A few other things to check:
-fuses (2 in trunk, one on head unit, one on radio unit); honestly don’t think it is this as everything is functional in another vehicle but for thoroughness
-LCM as it handles the I/K interface
-X596/939 plug under the glovebox


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[thumpin1]

Thank you. I will check these items tomorrow. I already checked the fuses and all were good. I didn't remove the head unit and radio unit because all works whenever it comes on. But as an update from a few days ago, I disconnected the battery and later reconnected it and drove the car with the issue of no sound. The radio did not come on until the next morning when I started it up to go to work. It immediately came on in key position #2 before I actually started the car. It was perfect and absolutely everything worked. I will check the items above on tomorrow evening. But if the radio ever revert back to the problem then I will chalk it up as a gremlin and just accept that it will work when it wants to.