Gents I'm t/s ing the amp/rear door speakers not working but my chiltons book does not detail circuits . I expect the amp to be powered when the radio is turned on but it would help to have a diagram to trace the power source. I will share a virtual scotch with the provider of a scanned/emailed diagram to nozel99 at hotmail dot com . The radio is an aftermarket Panasonic CD player connected to truck using a supplied connector specific to the Suburban harness with the front and rear speakers working as they should. The closest info I have found is a generic GM radio connection with a pink(ant) wire at terminal 8 of the power connector. There is no pink wire at the amp conector under the driver seat which begs the question: Is the amp poweed via relay'd circuits? Rolf