2003 Suburban K-1500 LS
I have an RPM-related harmonic noise from passenger-door rear speaker. It’s been there for quite sometime and can’t pinpoint when or why it might have started. The noise is only when the radio is on and the engine running and is only from the passenger-side rear door speaker. The pitch changes based on RPM. I had previously discovered that if I disconnect the Rear Audio Panel, (Radio Control - GM 15850811, discontinued, no longer available) leaving me with front speakers only, the noise is gone. But that also takes out the use of the DVD player.

Any ideas on how to diagnose the actual problem… is it the Rear Radio Control, a grounding issue to the radio or at the Rear Radio Control, the rear speaker, etc?

Thank-you
rjdjbd