having issues with anti theft security turning a 2003 chevy silverado from staying on

Yo may try removing positive cable from battery,with key not in truck,leave off for at least ten minutes,then place key in truck turn to the on position and replace battery cable,then turn key on and off three time,s before trying to crank,if this don,t work you may have to have key reprogrammed by dealer.

Put the key in the ignition, turn key to on position and leave it on until the security light goes out. Usually 15min. Once this happens crank the truck without turning the key backwards, just turn to start. This will reprogram the transponder from the ignition switch. Chevy does not have a chip in the get but the key acts as contacts between two points in the switch.

my 03 chevy z71 is getting fuel and it turns over but no crank.replaced fuel filter.but i noticed the security light on it shows locked could that cause it not to run

I'm having similar issue in my 2003 Siverado 1500HD.. driving down road and it died.. tried getting start then noticed theft light.. ran diagnostic and came back theft mode... have has plenty of people tell me this and that none that I tried work.. had a guy who says worked for GM before said it's a fuse in the panel by drivers door.. couldn't remember which fuse but it's a smaller one and it won't be blown.. pull it and it will disable theft mode... any idea which fuse it would be or how I can get it out of theft mode and back on road. Thank you all for your help