Anti-theft light on after removing the dash?

When you removed the dash did you plug back in the main electrical connectors? There are grounds wires as well that need to be hooked up so please recheck your work. Also have you checked the fuses with the key on.

Here is a guide to help:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

We should run the codes if the fuses are good. I would do a CAN scan which is easy to do, you can get a CAN scanner (Controller Area Network) from Amazon from about $32.00.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Amazon CAN scanner Link.

https://amzn.to/3G7mpFP

You can try a hard reboot which is done by removing the negative side of the battery, with the cable loose from the negative side of the battery, hold it to the positive terminal for 1 minute this will discharge the memory capacitors in the BCM and PCM allowing the system to reboot. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem.

When you try to crank it over does the security light flash? If not that might not be the problem it is flashing then yes, it is in lockout mode. Here is information on the security system that can help.

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

10-MINUTE LEARN PROCEDURE
1. Connect the Tech 2 to the vehicle.
2. Select Request VTD Info. For SPS under Special Functions in the Body Control Module menu.
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.
6. Start the engine. The vehicle has now learned the Passlock(TM) Sensor Data Code and/or password.

Let me know please.

Okay, that is normal. When you installed the new key lock were the keys programmed to the truck? If not, this will be the problem. To be sure let's do a CAN scan which will come up with a code. You can get a CAN scanner (Controller Area Network) from Amazon from about $32.00.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Amazon CAN scanner Link.

https://amzn.to/3G7mpFP