98 Blazer shut downs immediately after starting

I have a 98 blazer that keeps shutting down a few seconds after starting. I have confirmed the fuel pump works. I took it to a mechanic and he scanned it. It keeps saying to relearn/reprogam the security system. He has tried multiple times without success. He then thought the lock cylinder sensor needed replaced. Still no success. The security lights stays on and will not go out. Can any one help me get my blazer running?

i'm not a mechanic at all but i had a similar problem with my blazer besides the security light thing. it was starting and quiting until it wouldn't start anymore. turned out it was the fuel pump. the fuel pump was working and turning on but it wasn't getting enough pressure. it was getting 15lbs. and is supposed to get 60lbs. i'm actually getting sick of dealing with my blazer, i joined this forum to see if anyone could help me figure out whats the deal with my 4wheel drive, now i've been thinking about selling it and getting an envoy. good luck brotha'

I have a 98 blazer that keeps shutting down a few seconds after starting. I have confirmed the fuel pump works. I took it to a mechanic and he scanned it. It keeps saying to relearn/reprogam the security system. He has tried multiple times without success. He then thought the lock cylinder sensor needed replaced. Still no success. The security lights stays on and will not go out. Can any one help me get my blazer running?

What was the code no?
Does the security light go out or stay on after key on?

The relearn is key on and just bump started and then back to on for 10 minutes and untill light goes out.
Then key off then on for another 10 minutes untill light goes out and key off then on for another 10 minutes untill light goes out then off and then start it up.
Always keep a battery charger on it when relearing.

Has anything else been repaced?

Thank you to all who have replied with suggestions. I was able to get it running. It turns out the signal from passlock and the BCM was screwed up. The connections were bad. Thank you again.

You are welcome
And thanks for posting back how it went.
Glad you found the problem.