2001 gmc sierra speaker problems

hello two ? please. I just bought the panasonic CQ-C9700U and 2 sets of alpine type s speakers for the front and rear. well heres the problem when it gets to high volumes the sound will keep cutting on and off like theres a safety circuit cutting in or something. a friend told me i might have wired my speakers backwards but i cant find a wiring diagram for my truck anywhere. Right now im just using the darker colors as the ground but im not sure if that is right so i was wondering if you could mail me the color code and offer any advice as to what might be causing the problem.2001 sierra

If you have sound coming out each speaker. The problem might be the impedence. Check your speaker wire and see if you are getting a 4 ohm reading. If not there is your problem right there. Be careful whose advice you buy, but be patient with those who supply it.