Amp problems. i have a 1998 chev truck i just hooked a kenwood amp up to a pioneer premium cd

Question

i have a 1998 chev truck i just hooked a kenwood amp up to a pioneer premium cd deck,the amp only comes on when every thing is off,assoon as i turn the power on the amp shuts off.the deck seems to work fine and the amp just come out of my car it worked fine as well.the aux. and the main power work fine with the ignition when you turn the key forward and back words.the deck was already hooked up and the amp is hooked up proper.any solutions thanks