2023 Toyota Sienna
> Start by sitting in the driver's seat and closing the door. Buckle your seat belt. Turn the ignition to the "On" position without starting the engine. Within a few seconds of turning the ignition on, unbuckle and then re-buckle your seat belt three times, making sure each action is completed quickly. After the third buckle action, keep the seat belt buckled and wait for approximately 20 seconds. You should hear a confirmation sound or see a visual indication that the seat belt warning chime volume can now be adjusted. Use the volume control buttons on the steering wheel or the audio system controls to adjust the volume. Please note that the specific buttons or menu options for adjusting the volume may vary depending on your Corolla's trim level and audio system.
Worth a shot? Sounds like it’s adjustable (presuming Corolla and Sienna share some software) and yours is set a bit high.
Details vary from manufacturer to manufacturer, but they're quite common. https://lifehacker.com/hack-your-ride-cheat-codes-and-workar...
I'd do it too but... My car (not a Toyota), although 11 years old, is still on an extended manufacturer warranty (which I pay to renew each year) but if I modify the system, I void the warranty.
I'm just pointing out that out because Toyota have great warranties AFAIK and can be extended up to at least 7 years old? (if you do the maintenance at Toyota dealerships).
I want to "hack" my car too but I'm not doing it as long as it's still under warranty.