Why is no sound from radio or cd player even though I turn on the radio.

bad radio or loose connection.

Possibly, the bundle that goes through the door also have speaker wires in them. Check there.

SOUNDS TO ME LIKE FAULTY ALTERNATER AS WHEN ENGINE IS RUNNING ALTERNATER PRODUCES THE POWER NOT THE BATTERY

blower motor ..this pushes the air thru the duct work

Sounds like the battery might not have enough power to start engine. Even though, the radio might play and the lights may come on does not mean there is enough power to start engine. Try charging or jump starting it. These are simple tests to see if it is the battery. If the car starts after charging or jump starting, it was most likely the battery. Just let the car run for ten or so minutes before shutting off to charge the battery. Hope this helps

CODIGO FOR RADIO

Have you check the mute mode, maybe it is in mute mode.

if its factor bad radio is fried same goes with after market radios the only solution with out spending money to find out is to find a good used factore or get new after market your choice

sounds like your car has the multi function steering wheel, i know on the 7 and 5 series they come out of sync, im not sure why.
its about £75 to get plugged in at the dealers and they reprogram it, sometimes i have had the odd car with a damaged slip ring, it does all sorts of things, 1 in particular kept on beeping the horn,
i would say if u got 1 urs got upset when battery flat.

GM had insturment cluster problems 2003 to 2006 . Inside is a part called a stepper motor , this stepper motor controls the gauge position .
How to repair GM Instrument Cluster Speedometer Gauge Stepper
Beside's the stepper motor issue there can also be a problem with something called silver migration , this has to do with the solder used in the insturment cluster . This can cause a number of electrical problems most people would not even think possible .
Silver Migration
Watch this two videos .
Chevrolet Truck Battery Dies Overnight Part
Chevrolet Truck Battery Dies Overnight Part II