I'm going through this right now. After getting bad information (a rarity) from Crutchfield, I figured out that the factory Sync/Nav/DVD system DOES have an amp that is under the dash, to the left of the steering column. If you try to get the speaker level outputs from the back of the OEM head unit like I did, they are unamplified and will not be strong enough for a line level converter. I'm installing an Audio Control DQL-8 and after thinking the unit was defective, I called them and talked to their tech guy. He assured me that my problem was from a low level speaker input. He was right on. That said, the best place to tie into the factory wiring is at the amp. It's really tight in there, but with the driver's seat removed, I can lay on my back and get to the wires to patch in the new wires to the line converter, and then the new wires from the amp back to the factory harness so the amplified speaker signal goes through the factory wires to the speakers.
Last edited by thedynoguy; 01-21-2012 at 03:35 AM.
Reason: more info