I Have a 2006 Civic Hybrid. No nav system. I want to add a powered subwoofer in the trunk for thumping bass. How do I go about wiring it to the existing factory sound system? Do I need a factory service manual with wiring diagram? Thanks everybody.

 

First off, buy your amplifier and subwoofer.. get an amp wiring kit <-- those usually have instructions..
not sure if the stock headunit has RCA outputs but if it does, then you should be fine with the stock headunit.. Blue wire is remote, the rest is pretty much obvious.

 

If you don't want to run rca's or your stock headunit doesn't have the outputs, most powered subs have a hi-input connector that you have to wire in to your stock speaker wires. RCA's are a lot better quality.