> 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.