Try to start the truck, must wait ten minutes

voltage regulator is in the alternator
https://www.youtube.com/results?search_query=2003+GMC+Sonoma+truck+voltage+regulator
try the above link to YouTube and view relevant vids

Do a reset. Turn it on for ten minutes, off for thirty seconds. Try to start. There is also a relearn procedure. Do this three times, try to start after the third time. Have it on a battery charger. After that you need to have t scanned for codes. Code readers don't read security.

Do a relearn. 10 minutes on, 30 seconds off, 3 times . then try to start.

moisture in harness connections
spray with a silicon spray after you used compressed air to dry out everything

Check the fuel injectors, with the key on one side of the two wire connector will have battery voltage, if none is present then check the ECM fuses in the underhood fuel box.

Hi, if you have an aftermarket remote car starter installed, this could be defective, causing this issue. otherwise, there is a lock case that the lock cylinder turns in this cae contains the resistor sensor for the passlock, and could fail, and cause the security system to disable.If this has happened currently, I would scan the system for faults. Good luck...Coop

Smell of the oil,to see if the fuel injector(spider)is leaking into the crank case,if so,the intake will have to be removed to repair the problem,oh,and change the oil.

check theft system for problems with program(dealer)..disconnect battery for about five minutes,reconnect and try to start,if starts and then stalls leave key on for ten minutes exactly...then turn key to off position for 15 seconds..then start...if starts allow to run for ten minutes..

try replacing the throttle position sensor

Sounds like an engine sensor, EGR valve or O2 sensor has failed. First thing to do is to look at the engine trouble codes to pin down the failure. You can usually borrow an OBD1 code checker from your local parts store.