I have a 2003 Outlander that came with the standard radio. I bought an Infinity system(radio,amp,and din cable) that was taken out of another Outlander. I plugged the amp into the plug that is under the seat. I plugged the radio into the wire harness and connected the din cable from the amp to the radio. The radio powers up but no sound comes from the speakers. Does anyone know what I might have done wrong? Thanks