We have a 2007 Silverado 1500 LS 2WD 5.3 (new body) that I bought used with 47K miles for my teenage son back in April.
When we got it, it had an aftermarket alarm system already installed in it, so we did not get an original fob ... just the one supplied with the alarm.
In addition to the alarm, someone has done a manual-to-power-window conversion, and installed an aftermarket stereo.

I'm having a few electrical problems with it ...
1) Sometimes at start-up, when turning the key to the "Run" position, it does not engage the starter. Dash lights, stereo, dome light ... everything works ... except it will not crank. Funny thing is, if you tilt the column down, or sometimes turn the key on and off 2-3-4 times, it will then start as normal.
2) Sometimes when you start it, it will fire for a moment, and then die. It sometimes takes 5 to 15 starts to get it to idle on its own. And during this problem period, pressing on the gas pedal yields NO response from the engine at all ... just starts for a moment and dies.
3) Sometimes, while driving, the theft deterrent light on the dash will illuminate. When the light is on, the turn-signals will not work, and neither will the hi-beams. The light will sometimes turn off by itself after a few minutes, other times will stay lit until you turn the truck off. But when you restart the truck, it will usually stay off.

Notice I've used the word "sometimes" quite a bit ... that is because these problems occur sporadically. The only one that seems consistent is scenario #1 with the "no start" problem.

Thinking scenario #2 was a mechanical problem, I've looked at engine wiring, mass-air-flow meter, etc ... but the more I read, the more I believe it might be related to the theft deterrent system (as the posts I've read about problems related to this system seem to sound very much like the one I am experiencing).

We have since disconnected and removed the "brain box" for the aftermarket alarm ... but these problems still persist.

In speaking with friends (car guys), we believe it may be possible that scenario #1 may be caused by a wire from the aftermarket alarm tapped into the exciter wire for the starter (ignition kill) that is causing a bad connection ... hence the problem "curing itself" when the column is tilted downward.

But the theft deterrent light coming on and causing other electrical failures still baffles me. And the "start-then-die" scenario sounds like it also theft-deterrent related ...

I want to go under the dash and remove all remnants of that aftermarket alarm, but not sure if that will cure the problem if it is related to the FACTORY theft system.

Should I also consider it could be a problem with my key (it is a factory key with the + sign and black end) ... or should a get an original fob and a new key and try to see if that cures any of these problems?

I am bound and determined to figure this thing out ... with a little help from my friends, of course.

Thanks in advance ....