Passlock indicator on truck won't start?

With the Tech 2 scan tool, clear any DTCs.
30 Minute Learn Procedure
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; after approximately 10 minutes the telltale 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 on 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.
With a scan tool, clear any DTCs, if needed. History DTCs will self clear after 100 ignition cycles.

If the Passlock indicator is on, and your 2004 Chevrolet Avalanche won't start, it indicates a potential issue with the Passlock system. The Passlock system is an anti-theft feature that is designed to prevent unauthorized starting of the vehicle.

Here are some troubleshooting steps to help you resolve the problem:

Check the Key: Ensure you are using the correct ignition key for your Chevrolet Avalanche. The Passlock system is sensitive to the key's unique resistance. If you are using a spare key or a key that has been duplicated and not programmed correctly, it may cause issues with the Passlock system.

Check Battery and Connections: Verify that the battery is in good condition and fully charged. Check the battery terminals and connections for any signs of corrosion or looseness. A weak or poorly connected battery can affect the Passlock system's operation.

Reset Passlock System: Try performing a Passlock system reset. To do this, turn the key to the "ON" position and leave it there for about 10 minutes. After the 10 minutes, turn the key to the "OFF" position, and then try starting the vehicle. Sometimes, the Passlock system may relearn and allow the vehicle to start after a reset.

Security Light Behavior: Pay attention to the security light on the dashboard while attempting to start the vehicle. If the security light remains on or blinks rapidly, it may indicate a problem with the Passlock system.

Scan for Trouble Codes: If possible, use an OBD2 scanner to check for any trouble codes related to the Passlock system or other engine issues. The scanner may provide additional information that can help pinpoint the problem.

Yes, it could be the passlock sensor causing the problems.