Passlock flashing; truck will not start - 2005 Chevrolet Colorado

I think you have the GM PassLock system? Having a new key or disconnecting the battery disconnects the links between the key and the ECM. This explains how it works, to give you the background for fixing it.

https://www.fixya.com/cars/r29887709-gm_passlock_security_system

To reprogram PASSLock I ignition lock:
Step 1. After replacing the lock, try to start the vehicle with a correctly cut key. There is a one in 10 chance that the car will start.
Step 2. If the new lock does not match the electronic value in the vehicle's computer, an indicator light on the instrument panel will begin flashing and the car will be disabled.
Step 3. Leave ignition in the ON or RUN position.
Step 4. After approximately 10 minutes, the light will stop flashing and remain ON. The onboard computer has then been programmed to accept the new lock's signal. The car can be started.
If the indicator light turns off, the vehicle is probably equipped with a PASSLock II system. Continue with the following programming procedure.

To reprogram PASSLock II ignition lock:
Step 1. After replacing the lock, try to start the vehicle with a correctly cut key. There is a one-in-10 chance that the car will start.
Step 2. If the new lock does not match the electronic value in the vehicle's computer, an indicator light on the instrument panel will begin flashing and the car will be disabled.
Step 3. Leave ignition in the ON or RUN position.
Step 4. After approximately 10 minutes, the light will stop flashing and turn OFF.
Step 5. Turn the ignition on and back to the ON or RUN position.
Step 6. After approximately 10 minutes, the light will stop flashing and turn OFF.
Step 7. Turn the ignition on and back to the ON or RUN position.
Step 8. After approximately 10 minutes, the light will stop flashing and remain ON. The onboard computer has then been programmed to accept the new lock's signal. The vehicle can now be started.

Occasionally, a PASSLock-equipped vehicle will have problems starting. The following information can help to determine the cause of the problem.
The PASSLock system does not disable the starter; it only disables the fuel after the engine has started. If the vehicle will not crank, PASSLock cannot cause this condition. If the vehicle starts, but stalls quickly, this condition can possibly be related to PASSLock.

Most PASSLock-equipped vehicles have a telltale indicator in the instrument panel. When a PASSLock-equipped vehicle is being started, the instrument panel warning light for PASSLock remains on until the engine starts. For this reason a "No Start" condition should not be confused with PASSLock System fault.

..

you dont bypass /hotwire system thats movies has the new ignition parts been flashed to your vehicle

This an example of relearn procedure.
Clear all codes.
start the engine or try to.
The system long tamper mode and security lamp will flash for ten minutes
Leave the ignition switch in the run position until the lamp stops flashing.
Turn ignition switch to off, turn ignition switch back to the run position.
The theft system lamp will flash again as the system learns. When the lamp stops flashing, the learn cycle is complete. Some info says to use battery charger on low setting because this procedure can take a while. The passlock key is just a mechanical key, no pellet, no transponder. It's the tumbler that communicates with pass lock sensor not the key. If the relearn doesn't work, I'm not sure what to tell you?

I read your problem, and I think Reliable-Store has the solution of your problem, Just visit the link I attached here, I'm sure you will get the solution of your problem forsure. Best Manuals

Is there a security lamp on the dash that is on or flashing? Any applicable trouble codes? My info shows you have passlock, usually a fuel injector disable, only, may start and stall. If vehicle starts and stalls, leave key in the on position, If security lamp does not flash, the passlock system should not be at fault.

Need to turn off passlock - Chevrolet - iFixit

https://www.ifixit.com/Answers/View/.../Need+to+turn+off+passloc...

iFixitThose of you that have stalling problems, it is not passlock. ... traction fault on the display when it shuts down or won't start and have to wait my 10 min to restart.

GM Passlock Security Light Issues - RepairPal

repairpal.com/gm-passlock-security-light-issues

If you find yourself stranded, your engine won't start, and the security light is flashing, ... The most common repair is to replace the ignition lock cylinder or Passlock ... The warning light on the VATS system is similar except it does not have the ...

No Start Due to Failed Passlock Sensor : Pontiac Grand Am ...

repairpal.com > Problems > Pontiac > Grand Am

Here's a link that will help you out. This is a pretty common and expensive problem in GM vehicles.
http://vatspasslockpasskeysecurityhelp.yolasite.com/

If the light is flashing it may be an issue with the passlock sensor.Here is a process you can try to reset the passlock. If this process does not work you may need to replace the ignition tumbler and passlock.
PASSKEY LOCKOUT RESET ALL GM CARS 1999 AND UP
1) Put the key in the ignition and turn to the "ON" position. Leave it that way for 10 minutes. After 10 minutes turn the key and take it out. Repeat this process (2) more times (3 times, 30 minutes total) This should reset the PASSKEY system to recognize your key.

does it start at all, or does it run for about 1 second and shut off? if the latter, then it's the passlock system, and he could have a defective key or security module. the keys have a predetermined resistance value which activates the passlock system to prevent hotwiring. If it is the passlock system, then sometimes you have to wait 15-20 mins for it to reset before starting the engine.

It is your locks. I would just disconnect them and lock the car manually. Its a common problem on most GM cars cause water got in an rusted the auto lock motor cause them to send the wrong signal to the computer.