I am trying to install an after market radio and system in my 1997 suburban. I have everything installed properly (amps, cross overs ,et)c and when i plugged the new radio in only my drivers side front speaker goes on. Is there a factory amp or something in the truck I am missing? Wiring harness is all plugged in correctly. Speakers work fine with factory radio unit plugged in. Any ideas would be appreciated... Thanks...