check all fuses.. should be a 15 amp.. with a test light or volt meter.. after that with volt meter or test light.. check for power in all the wires that are cut.. you should have 2 that has power with key on engine off.. turn key off then check again should be one with 12 volt power.. mark that one because that's going to be you red wire on your aftermarket radio.. your yellow is the other one that comes on with the key on !! hope this helps.. as far for speakers ill let you know as soon as you let me know how you did in finding power..
