How to reset aftermarket adapter for 02 Impala.

So I unplugged my battery to install a new amp and when I plugged it back in, my kenwood aftermarket stereo won't turn on or anything. When I originally had the deck installed they had to also install a new wire harness and head unit adapter. Believe it or not this same thing has happened to me before except I had taken it into best buy and the tech basically said that the adapter needed to be reset. I watched the guy fix it in literally 30 seconds but I don't know the sequence of events to reset it. Anyone here have a clue? I've looked everywhere online!
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Answers
http://www.impalaforums.com/chevy-impala-7th-gen-discussion/328153-aftermarket-radio.html
Go to amazon or whatever vendor you prefer, search for Scosche GM06B.
If you have steering wheel audio controls, they also make an adapter for that from Pac-Audio so you can continue to use them. The harness is 17 feet long that lets you relocate (the factory radio) in the trunk, which I did and I'm still able to reset the oil reminder light, the TPMS light, and any of the other stuff from factory. I hid mine along the passenger side behind the carpet with some brackets, and it works like a charm. I will post some pics if I get a chance.