02 silverado check engine light

[salrod00]

i just purchased a regular cab with a v6 vortech motor in it. the check engine light is on and i went to three different autopart stores to check it out. the problem is that they cant even download the info into the code reader. they plug it in but the code reader doesnt even turn on. they told me to check the fuses and my wiring to see if something is disconnected or not. anyone has a clue why it would not send any signal to the code reader. the truck stall a little bit .