1999 Blazer...

Opened pass door, hit unlock, all doors except drivers unlocked, reached over put key in ignition tried to start car, started, ran couple seconds and died...

Then did the relearn procedure... Car would start every time, however if I tried to unlock doors from the pass side, car would start run 2 sec and die, have to do relearn over again... As long as I unlock the drivers door first and try to start car starts every time... Never had a problem before by unlocking from pass side which it normally the way do it so can put child in car seat in back... Any ideas? Also Security light is always on when vehicle is running...

 

The big clue here is that it works correctly from the driver door.


The BCM, (Body Control Module) is not receiving the unlock signal from the passenger door lock cylinder switch. Passlock interprets it as a theft, and disables the injectors after ~ 2 seconds. That's probably what's causing the "SECURITY" light to remain on when the engine is running too. Relearn will not do anything for this problem.


EDIT: The BCM "knows " the doors are locked and the system is armed. When you enter through the passenger door, all it "sees" is the dome light come on, and then the doors are unlocked. Perfect example: Rock through the window, reach in and open the door, and unlock the doors using the power locks. System is doing what it was programmed to do. If you have keyless entry, using the key FOB should circumvent the problem.