I have a 1991 ford taurus lx that has premium sound that the factory put in. I bought a pioneer DEH-P38oomp. I didnt buy a wiring harness because i forgot about it so we tried to splice the wires together. Can i do withought the harness? So we spliced the wires together and got power and could only hear a faint sound in the front passenger door speaker. What did we do wrong because we had to turn the volume all the way up to hear anything. Also what would the diagram be for the car speakers?