I have a 2003 Tahoe with the stock stereo. When I bought it, there was an auxiliary cord installed to connect to an iPhone. When the source was set to AUX1, I could play music through the stereo.

Yesterday, I randomly couldn’t set the source to AUX1. Whenever I would select it, after a few seconds, it automatically changes to AUX2. The cord still charges my phone, but won’t play music through the stereo.

Suggestions?

 

No expert on such things, but disconnecting the battery couldn't hurt. Might reset something. Most of us don't get into radios and audio systems all that much.