Security light on why?

Hello, I'm Danny.

How about trying our sites anti-theft, security system reset. Here is the tutorial:

https://www.2carpros.com/articles/how-to-reset-a-security-system

After reading just scroll the page to find Chevrolet. Let us know what happens and we'll go from there. Hope this helps and thanks for using 2CarPros.

Hello again.

Please do a reboot

https://www.2carpros.com/articles/step-by-step-guide-performing-a-hard-system-reboot-for-your-vehicles-electronics-systems

Danny-

If you have a spare key try it. If not try cleaning off that key where the pellet is and try again. I would do a hard system reboot, remove the negative battery cable and hold it to the positive post for 1 minute then reconnect. This will discharge all capacitors so the system can come back online. This guide can help as well.

https://www.2carpros.com/articles/how-to-reset-a-security-system

Please run down this guide and report back.

There is an error in the security system module.
Get it checked for trouble codes and come back if you need them translated.

GM PASS LOCK RELEARN- Ignition to "run" position, try to start and let key return to "run" position
Approx ten minutes security light will go off
turn key "off" and wait 5 seconds
repeat 2 more times for a total of 3 relearns.
Turn key off, then start it

Good afternoon,

It sounds like the key has forgotten the password.

I assume you removed the battery cable. This is common when the cable is removed. I posted the re learn procedure below.

Roy

PROGRAMMING REPLACEMENT PASSLOCK(TM) SENSOR, BCM, OR PCM

IMPORTANT:
The body control module (BCM) must be programmed with the proper RPO configurations before performing learn procedures. See Body Control Module (BCM) Programming/RPO Configuration.
If replacing the BCM with a GM Service Parts Operations (SPO) replacement part, the module will learn PASSLOCK(TM) sensor data code immediately. The existing PCM however, must learn the new fuel continue password when the BCM is replaced.
If replacing a PCM with a GM Service Parts Operations (SPO) replacement part, after programming, these modules will learn the incoming fuel continue password immediately upon receipt of a password message. Once a password message is received, and a password is learned, a learn procedure must be performed to change this password again. A PCM which has been previously installed in another vehicle will have learned the other vehicle's fuel continue password and will require a learn procedure after programming to learn the current vehicle's password.

CONDITIONS
Use this procedure after replacing:
Passlock(TM) Sensor
BCM
PCM

LEARN PROCEDURES
There are two available methods to perform the programming procedure:
A 10 minutes procedure which requires a Tech 2 and a techline terminal.
A 30 minutes procedure which does not require the use of any tools.

10 Minute Learn Procedure

TOOLS REQUIRED
Tech 2
Techline terminal with current Service Programming System (SPS) software

1. Connect the Tech 2 to the vehicle.
2. Select "Request Information" under "Service Programming".
3. Disconnect the Tech 2 from the vehicle and connect it to a techline terminal.
4. On the techline terminal, select "Theft Module Re-Learn" under "Service Programming".
5. Disconnect the Tech 2 from the techline terminal and connect it to the vehicle.
6. Turn ON the ignition, with the engine OFF.
7. Select "VTD Re-Learn" under "Service Programming".
8. Attempt to start the engine, then release the key to ON, vehicle will not start.
9. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF, the vehicle is now ready to relearn the PASSLOCK(TM) Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK.
10. Turn OFF the ignition, and wait 5 seconds.
11. Start the engine, the vehicle has now learned the password.
12. With the Tech 2 scan tool, clear any DTCs.

30 Minute Learn Procedure
1. Turn ON the ignition, with the engine OFF.
2. Attempt to start the engine, then release the key to ON, vehicle will not start.
3. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF.
4. Turn OFF the ignition, and wait 5 seconds.
5. 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(TM) Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.

IMPORTANT: The vehicle learns the PASSLOCK(TM) Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.

6. Start the engine. The vehicle has now learned the PASSLOCK(TM) Sensor Data Code and/or password.
7. With a scan tool, clear any DTCs if needed. History DTCs will self clear after 100 ignition cycles.

I do not understand what you are saying "it will stay cranked"? Does it start, run then shut off? The security will shut down the fuel pump. Try this to see if it will relearn the key:

1- Turn key to 'run" position, try to start and let key return to "on" position.
2-After approximately ten minutes the security light should turn off.
3-Turn ignition to "off" position and wait five seconds.
4-Repeat steps 1-4 two more times for a total of three cycles equaling thirty minutes.
5- Start engine.

These trucks had problem with the BCM which is the car alarm. Here is the location so you can replace it, but you will need to have it programmed to the truck before it will run. The cost is about $130.00.

On the lower left side of the I/P below the steering column.

Check out the diagrams (below). Please let us know what happens.

Cheers

Have you done a relearn on the pass-key?
Gm pass lock relearn- Ignition to "run" position, try to start and let key return to "run" position.
Approximately ten minutes security light will go off.
Turn key "off" and wait five seconds.
Repeat two more times for a total of three relearns.
Turn key off, then start it.