PassLock, is not something you want to guess at, can get to be expensive....

One thing you can try:

Apply e-brake(this keeps auto lights off)......make sure you have a well charged battery....if not, add a jumper box across the battery....

Thgis is a procedure I found online:

Turn ON the ignition, with the engine OFF.
Attempt to start the engine, then release the key to ON; the vehicle will not start.
Observe the SECURITY telltale light; after approximately 10 minutes the telltale light will turn OFF.
Turn OFF the ignition, and wait 5 seconds.
Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes; the vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.
Important: The vehicle learns the Passlock Sensor Data Code and/or password XXXXX the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
Start the engine. The vehicle has now learned the Passlock Sensor Data Code and/or password.

If this works, it is only a temporary fix.....the problem could be the PassLock sensor, BCM, or wiring/connections in between the sensor and BCM....

ok so I've tried this and it didn't work so I figure to check my injectors....the injectors are not letting fuel into the engine

But are you still getting a consistent security light???

Well sometimes it won't come on and sometimes it will

You need to find out what Passlock is bitching about. If Passlock is killing your injectors, you will spend all year long thinking its engine related. Ya gotta stop playing the guessing games. Get your truck scanned for body codes.

On another note, the 2000+ Chevrolet trucks were known for ignition switches going bad and causing Passlock/no start conditions. That happened on my 2000 Blazer.