I just recently purchased a Galaxy Three with 4.0.4. Before the new phone, I had an Apple iPhone 4S. When I plugged the iPhone's headset jack directly to my car receiver's Aux In it worked just fine. When I do the same with the Galaxy, it does not work. I plug one end of the standard 3.5mm male to male adapter cable into the phone it reacts as if a headset was connected - headset icon appears. The Galaxy reacts as if the cable is not present the moment I connect it to the receiver. The headset icon disappears and sound comes from the phone's speakers.
I do not have a bluetooth enabled car so that is not an option.