Are you using the proper harness to go between the Pioneer harness and the cars harness? I used a Metra 70-5521. Then make all of your connections here, then just plug it all together. DO NOT cut the factory plugs off the harness'. The only connections that cannot be made here are the VSS and the illumination. These locations can be found with a little bit of searching on your part, either here on this board or I also used mustangforums.com to gather alot of information. G/L.