I'm 100% sure that I have it narrowed down to the passenger's door speaker. I was running the head unit with one speaker, then adding the others one by one until it stopped working -- and that was the culprit.

I did trace the harness as far back into the dash as I could but could not find anything.

If a speaker is blown, would that have the same result??

For the few seconds that all the speakers work, I hear whatever is playing through my troubled speaker.. then it fades out as if it was a static-filled radio station... then all the speakers stop working.

This is the most frustrating damn thing in the world! Hahaha