Reset security system

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Does the engine crank and not start? Was anything done prior to this issue? For example, someone jumped started the car and reversed the cables?

Did you try ignition on for 10 minutes to see if the anti theft light turns off?

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

The BCM can be causing the issue as well as the theft control module. To eliminate the theft module from causing the BCM problem disconnect the Low Speed LAN coming from the Theft Module at the C3 connector PIN 10 and recheck BCM communication. Visa-versa for the theft module to see if it's the BCM shorting the theft module.

Let me know what is happening.

Take care,
Joe

Your passlock system (theft deterrent system) is triggered.
Try to reset it:

-Turn key like you're gonna start the car
-let key back in the run position until the security light stops flashing (about 10 minutes).
-when security light turns off, turn key to OFF for five seconds
-turn key like you're gonna start the car again and repeat the same procedure for another two times (3 relearns total, about 30 minutes)

On the last relearn turn key to OFF for five seconds like you're supposed to, then on the next attempt to start the car the system will 'relearn' the passcode/proper resistance, and your car should start.

If it doesn't work, you'll need to have your car checked at a dealer; you may have a defective passlock sensor, bad connection at the BCM, bad ignition lock cylinder/switch.

Also, I'm not sure, but the owner manual may have the relearn procedure in it. You may want to check.

Hope this helps

Ignition switch need to have it replaced if you get stuck and will not start for you turn key ON for about 10 min and you should be able to start after that plus check this guide out to help reset the system

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

let us know what happens

The official GM passlock relearn procedure is as follow:

1. Turn ON the ignition, with the engine OFF. Attempt to start the engine, then release the key to ON (vehicle will not start).
2. Observe the SECURITY light, after approximately 10 minutes the light will turn OFF.
3. Turn OFF the ignition, and wait 5 seconds.
Turn key to START; sometime your car will start after only one relearn. If so ,you're done. If not, repeat steps 1 to 3 two more times (for a total of 3 relearns). A that point, the vehicle will be ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to START.

Important
The vehicle learns the Passlock 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.

This guide can help as well

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

Hope this help

You may have to do the reset a twice or three times electronics are funny if it still will not start you will need a pro scanner to see what the problem is. here is our dandy little link to help.
https://www.2carpros.com/articles/how-to-reset-a-security-system

Is your security light blinking?
Have you tried the GM passlock relearn procedure?

-turn your key to 'start' and let key go back to 'run'
-wait until the security light goes off (about 10 minutes)
-turn key off and wait 5 seconds
-repeat same procedure two more times for a total of 3 relearns.

On the third time, after you turn your key off for 5 seconds and turn it back to 'on', your system relearn the code and your car should start.

If it doesn't work, you may need to get a new passlock sensor, or possibly a new ignition switch/lock cylinder. Take it to a dealer and tell them about your problem. This no start condition due to the passlock system is very common. I just want to let you know in case the dealer tells you he never heard of it.

Your problem is probably your theft deterrent system. This is a very common problem on chevy cars (and others for that matter). Here are some solutions I gave someone else on this site with the same problem:
* Go to a dealer and get charged a ridiculous amount of money for a diagnosis and a fix that may or may not work.
* Try the GM reset procedure for passlock:
"Â Turn ON the ignition, with the engine OFF.
"Â Attempt to start the engine, then release the key to ON; the vehicle will not start.
"Â Observe the security telltale; after approximately 10 minutes the telltale will turn OFF.
"Â Turn OFF the ignition, and wait 5 seconds.
"Â Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the car may start after only one time though); 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 on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
* Bypass the system (check online for infos)
* Attempt to fix it your self, in which case you'll have to determine what's wrong: passlock sensor, ignition cylinder, BCM, bad connection, etc

Relearn procedure below.

Roy

PROGRAMMING THEFT DETERRENT SYSTEM COMPONENTS

PROGRAMMING REPLACEMENT PASSLOCK SENSOR, BCM, OR PCM

IMPORTANT: The body control module (BCM) must be programmed with the proper RPO configurations before performing learn procedures. Refer to Body Control Module (BCM) Programming/RPO Configuration. See: Body Control Module > Programming and Relearning > Body Control Module (BCM) - Programming/RPO Configuration

IMPORTANT: If replacing the BCM with a GM Service Parts Operations (SPO) replacement part, the module will learn Passlock sensor data code immediately. The existing PCM however, must learn the new fuel continue password when the BCM is replaced.

IMPORTANT: 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 any of the following:
- Passlock 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 SPS (Service Programming System) 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 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

TOOLS REQUIRED
None

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 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 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 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 am an auto tech and I had an impalla in my shop that did exactly the same thing. I tried everything. To make along story short I took out the radio and found the security wire on the radio plug and cut the wire. Starts every time now. No more problems. Repry to this answer and I will tell you how to do it. Jerrygoodwrench.

First thing you need to do is see what code's you have in your body control module then go from there. Most common thing to go wrong is the pas lock sensor's. It's not the easiest thing for a do it your selfer to fix. Because you need a advanced scan tool that can read body control module code's and live data from the body control module to see what the pass lock reading's are when the car isn't starting.