security?

try resetting anti theft unit first see pic. if not that then check fuel pressure with a gauge, auto parts rent them.

https://www.2carpros.com/articles/how-to-reset-a-security-system

Check out the diagrams (Below). Please let us know what happens.

its 5.3 v8 cranks but wont start. starts fine when its warm. security light has been coming on

Your Passlock system module has a problem. A dealer must trouble shoot this system because they have the diagnostic scanner to do so...

background: car runs great, when it feels like it.

have multiple IPC issues w/ various CEL messages & faulty gas guage. gas gauge was on the funk for a while - just dealt w/ it using my trip odometer. now, i have delays in my ipc - shifting from park to drive, the gear indicator lights will vanish...temporarily. this too was just annoying.

now, i get faulty oil pressure warning w/ immediate car shut off - while driving sometimes. oil pressure gauge never indicates low/no pressure prior.

have a base model; no frills (only A/c & cruise).

only mention since one of the CEL warnings is prefaced w/ "security" message prior to engine cut out at 65 MPH. there is no security system on the truck.

engine cuts out & will not start again (until i try to start repeatedly, reset the engine oil change timer, or wait a while)

happening much more frequently nowadays.

There is what they call a Passlock system in your truck. It is a factory security feature NOT a security system. All of your symptoms point to a failing Passlock module or an ignition switch. There is an internal resistor in the ignition switch that sends a signal to the Passlock (security) module. If this resistor fails or is failing your engine will not start. Your oil pressure switch (electrical) circut is directly related to the Passlock system. If you do the following you can disable the Passlock system temporarily (to get the engine started)...
Turn the key on but DO NOT start the engine. Wait 6 to 9 minutes. Then turn the key off for 10 seconds. Then turn the key and start the engine...Unfortunatly the Passlock system must be serviced at the Chevy Dealer.

I tried to start the truck, after being home for a couple hours, and it starts right away, but immediately shuts down.

is there a security light on or blinking? do you have another key that you can try? it sounds like a possible security issue.

Replaced faulty light assembly(box in steering wheel)
When trying to start fires and runs for about 5 seconds.then dies. The message center keeps flashing security.

Hello .. thanks for the donation .. much appreciated try the passlock relearn process ! PASSLOCK(tm) SYSTEM AUTO LEARN NOTE:This procedure allows relearning of Passlock(tm) module or PCM/VCM learned data code after replacement of Passlock(tm) module, Passlock(tm) sensor or PCM/VCM. DTC B3031 will set when entering programming mode. Clear all DTCs. Turn ignition off. Replace component(s) as necessary. With transmission in Park (A/T) or Neutral (M/T), momentarily turn ignition switch to START position (engine will not start). Leave ignition switch in RUN position (engine off). If Passlock(tm) sensor was replaced, SECURITY indicator light will flash for 10 minutes. If Passlock(tm) module was replaced, SECURITY indicator light will flash for a few seconds, and then remain on for 10 minutes. If PCM/VCM was replaced with a new PCM/VCM, vehicle may start and procedure may not be needed. If replacement PCM/VCM was used even momentarily, SECURITY indicator light will flash for a few seconds, and then remain on for 10 minutes. After 10 minutes, when light turns off, turn ignition switch to OFF position for 5 seconds. Repeat step 2 twice more. Ignition switch must be turned to OFF position. Auto learn procedure will be completed during next start attempt. Clear all DTCs. If PCM/VCM was replaced, reprogram PCM/VCM. See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. hope this helps