Lost key fob, now alarm goes off no matter what?

Is the security light flashing? If so, it seems like the alarm is not disarming. I would do a CAN scan to see what comes up 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/3sX8MCX

Here is some information about the system:

Note: The security access procedure is used to obtain passive anti-theft system (PATS) security access. PATS security access must be granted to erase ignition keys, enable/disable unlimited key mode, set unlimited transponder key ID and enable/disable the spare key programming switch (PID SPARE_KEY). The security access procedure invokes an inherent 10-minute time delay prior to granting security access during which the diagnostic tool must remain connected to the vehicle. Once security access is granted, a security access command menu is displayed which offers various command options.

1. From the diagnostic tool, enter PCM. Select SECURITY ACCESS. This procedure takes 10 minutes to carry out, during which the ignition switch must be in the ON position and the diagnostic tool must be connected to the vehicle.
2. After the 10-minute security access procedure is completed, a new menu is displayed with command options. Select only those functions required before exiting out of this menu. Once exited out of this menu, the security access procedure must be repeated again to carry out additional commands.

Enabling Unlimited Key Mode

NOTE: Unlimited key mode is intended for use by those customers who need more than 8 keys for their vehicle.

1. The customer must choose an 8-digit, non-00000000 or 00000001 number to be programmed to all of their vehicles. All customer vehicles need to use the same number. Valid digits are 0-9 plus the letters A-F.

2. NOTE: If the PID: UNLIMITED TRANSPONDER KEY ID is not available, unlimited key mode is turned ON, and must be turned off before viewing the stored code. At this time, unlimited keys may be programmed to the vehicle. To view/change the stored code, follow the procedure for turning off unlimited key mode below.

Check the PID: UNLIMITED TRANSPONDER KEY ID and compare its value against the code chosen in Step 1.

3. Using the diagnostic tool, select PCM from the menu. Select SECURITY ACCESS to obtain security access.

4. Once in security access, if the Unlimited Transponder Security Key PID is 00000000 or 00000001, select Active Command: SET UNLIMITED TRANSPONDER KEY. Enter the 8-digit code chosen by the customer.
5. Select: ENABLE UNLIMITED KEY MODE.
6. Select: IGNITION CODE ERASE.
7. Disconnect the diagnostic tool and turn the ignition OFF.
8. Program 2 ignition keys to enable the vehicle.
9. Program any additional keys using either Key Programming Using Two Programmed Keys or Key Programming Using Diagnostic Equipment.

Disabling Unlimited Key Mode

NOTE: By disabling the unlimited key mode with a random 8-digit number the previous access code no longer operates the vehicle.

1. Using a diagnostic tool, select PCM from the menu. Select SECURITY ACCESS to obtain security access.
2. Select: DISABLE UNLIMITED KEY MODE.
3. Select: PROGRAM UNLIMITED TRANSPONDER SECURITY KEY.
4. Enter an 8-digit random number (not 00000000 or 00000001).
5. Select: IGNITION KEY CODE ERASE.
6. Disconnect the diagnostic tool and turn the ignition key to OFF.
7. Program 2 keys to enable the vehicle.
8. Program any additional keys using either Key Programming Using Two Programmed Keys or Key Programming Using Diagnostic Equipment.

To me it sounds like the Alarm Transponder has gone out here is how you can change it out in the images below in case you need it. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem.