No patches! All I did was plug in the cable adaptor that came in the box and ground the green parking brake wire. That's it! After installation I noticed that front, rear, and sub speakers work at any volume whereas the original factory installed HARMAN/BECKER radio only drove the rear & sub when set to high volume level, plus the sound level quadrupled! What was maximum volume on the factory radio is half volume on the Sony. When the Sony is set to maximum volume and music with extra bass played then my CrossFire vibrates the neighborhood!!! Of course, the neighbors don't like that so I only do it when driving on the highway.
Anyways, the factory amplifier works great when used with a radio like the SONY CDX-M9900.