1999 S10 Blazer 4.3L, 4dr 4WD. Truck starts but immediately shuts off. If I dribble gas into throttle body continue s to run. Suspected a passlock problem but the security light comes on when key is turned then goes off after a few secs. Start the truck it starts then dies, then the security light comes on for 2 secs then blinks one time then goes off. I pulled the ignition lock out and unplugged the passlock connecter on the ignition cylinder housing. used a screwdriver to rotate the ignition switch and get the exact same results. starts and dies one blink on security light. Anyone ever come across this failure before?
Thanks for any help or suggestions.

 

Sure sounds like a Passlock problem. Having the passlock disconnected doesn't defeat the system... I am not sure what you were trying to accomplish with that.

Try cleaning the terminals to the passlock sensor on both the sensor and the connector that plugs into it.

 

I'll give cleaning a shot. What I was trying to do is see if I could get the security light to blink like I thought it was suppose to do in a passlock problem. I get 1 blink with the normal key or diconnecting the passlock sensor and starting it without a key I get 1 blink. Every thing I read has said passlock failure will cause the security light to
blink for the passlock cycle of 10 mins.

 

Yep, had same problem with a 1999 we were working on for a car lot.

First replaced the computer with one I had on another vehicle. Started up & ran fine.

So then removed that computer and re-programmed the blazer's computer. No go.

Next, pulled the cover off the steering column and found the passlock connector wires cut!

Quick fix.