Get a line coverter. What you basically do is take the converter, which has 4 wires... one + and one - from the left, and one = and - from the right channgels. you splice this into your factory wiring. check out radioshack, they have these inline clamp down splice things, they are blue colored. The other end of the converter then gives you an RCA signal output in L & R form. Some converteres allow you to adjust the output while other's don't. You can pick up one of these converters for $20-30 in Best buy, circuit city, etc... or go to ebay and search up line converters and get one for 10-15.