HELP...Stereo install, now theft deterrent light on.

[buckeye88]

I just put a new head unit, along with amp & sub in my 06 Cobalt LS 5 speed. When I went to turn the ignition to test it, at first it would not start & the theft deterrent icon was lit up on the dash.
It finally started but the tach needle does not move, mnor does the speedo needle. Also the radio has no power, even when I hooked the old radio back up.
The owners manual is no help as it says to press a button on the keyless remote, which I don't have. I have 1 key, taht is a PASS-Key III so I can't try another as it suggests.
Anyone else had this issue? How do I get it back to normal?
I don't know if having part of the dash still apart has any effect on this or not, but I don't want to put the new head unit completely in if it won't work.
Thanks in advance for any help.

 

[YelloEye]

Disconnect the battery for ~30mins with the stock stereo and all the electronics hooked back up the way they were before you started, if all is back to normal when you hook the battery back up go one step at a time disconnecting the battery between installing things to see where your problem is.

 

[Mrslice2004]

are you using the Expensive 150$ harness or a cheap $20 one? If you have Keyless entry and all that, your most likely going to want the $120-150 GM harness. Otherwise u could lose all your door chimes, blinkers all that stuff, IF you have a base model cobalt , and just added Keyless entry then you should be fine with the $20 harness, Just make sure to get the one with a Seperate Accessory wire, and wire it to your Accessory part on your ignition. ill have to look up the harness #, been awhile.

 

[Posezion]

Check the fuses? Depending on how your system is rigged you may have blown a fuse or two. I ended up blowing my power steering when I was tuning my AMP one time (lol).