Truck starts tthen it dies imatiately - C1500 Chevrolet Cars & Trucks

See if fuse is blown tthen check power to fan if there is power then fan is bad

Check crankshaft sensor.

check brakes all wheels tthen check sensors if equipped in the pads flex hoses could be plugged to find out open bleeders as well the calipers could stick they all have to be cleaned and lubed so they work properly

check under the hood, if no tthen to the side of passsenger dash

The security light is a visual indication that something in the car's antitheft system is failing. In most GM cars and trucks there is a hidden system that most people are unaware even exists. From the moment you put your key in the ignition, there begins a constant line of communication between your key's security chip or transponder, to the ignition's lock cylinder, and then to the car's TDM. These 3 parts are in CONSTANT communication. If the key is in the ignition, these parts are sending signals to each other. The security light illuminates when that signal gets broken, even just for a second. When the signal breaks, the car goes into antitheft mode. The car thinks its being stolen or hotwired because it is not getting that signal from YOUR specific key. There is where the security light turns on and shuts down your vehicle.
http://vatspasslockpasskeysecurityhelp.yolasite.co

I have an idea. Check the compression of the cylinders when cold.

You can get the check engine light to turn off by unplugging your battery for about 10 minutes tthen plugging it back in or getting a scanner and erasing the trouble code. Hope this helps.

yes indeed you do, after the vehicle pumped up you can get down to the rear wheel and listen for air escapes from the air bags.
if there is no air leak then you have a solenoid that let air go back to the pump

It is going into what is called {limp in mode}. Have the vehicle scanned, it likely has a bad input shaft or output shaft speed sensor

Has fuel filter been change has gas tank been cleaned?