'03 SSEI with stock deck. Monsoon. Hooking up a Jensen amp with some subs. Have a hi lo switch (inverter) to connect RCA jacks to deck. Problem is I can't see a way to splice into the harness. It'* very tight right behind the deck and I can't see where it goes after that. Also need to know which wires to splice into. Anyone done this in their car? Any tips or suggestions? Any help greatly appreciated.....

There isn't a harness to tap into behind the radio. only a ribbon cable like the picture below. I would have to suggest tapping into the 6x9 wires in the trunk. this serves a dual purpose. 1. it'* the easiest place to splice into any existing wiring,
2. it'* already right there in the trunk. No need to run all that extra wire.

get an aftermarket head unit.

I want to keep the stock deck for now.

I was told if I tap into the rear speaker wires in the back I might get noise. Also I need to get to the harness anyway because I have to connect the light blue remote wire for the amp. Unless there'* another place for that as well?

there is not any connection to make for the remote turn on, the stock radio doesn't use such a thing in the traditional sense. the class II data system this generation of bonneville uses all data signals to turn the things on. For example, there is not a remote turn on lead that turns the factory amp on. The stock cd player sends a data signal that turns the amp on. The entire class II data bus can be a confusing system to get used to.

So I would have to tap into a hot wire else where? Maybe at the fuse block? Something that is hot when the ignition is turned on.

exactly

Mine isn't like that. In place of the ribbon thing, there is a wiring harness with a plug that comes in the back just like yours, everything else looks the same though. But the wiring harness is wound so tight and only has about a half inch showing.

Oh really? Hmm. definately get a picture of that if you can! I've honestly never seen that before. All the bonneville'*, and Auroras I've seen have the Ribbon cable. :?

some amps can sense when the music is turned on...and then they go on. Only works for speaker level inputs. Before you go taping into ignition stuff check the specs and see if you amp has that feature. If so there is no need for a remote wire.