What problem could be causing my truck to not stay started?

It stays on.

Go to YouTube videos and search Passlock, there is a lot of information to view and help you understand what the cause is. Is it raining there yet, just sprinkle here.

Ok. I'm gonna do that right now. Not raining here yet but it sure is lookin like its going to! I looked into the passlock thing. When you said security light for some reason I thought you were talking about the check engine light. Our truck doesnt have a security light. Its a 1990. But the check engine light stays on. Sorry about the confusion.

Sorry, had to go to the store. '90 model, didn't notice, was thinking or the symptom, just like a passlock issue. Not sure off the top of my head, you just fixed the TP sensor, maybe fuel issue or sensor, but without testing not sure. Can you read the code, and let me know.