Here is the procedure for turning off the seat belt chime in the Toyota Avalon (years 2005+). This may work on other Toyota and Lexus vehicles as well. Please note that seat belts should be worn at all times and this procedure is used at your own risk.
1) Turn the Car On, Do not start the engine (Leave your foot off the brake). Cycle your trip reset knob until it reads ODO (not trip "A" or "B"). Turn the ignition back off. Wait a couple of seconds.
2) Make sure seat belt is not fastened
3) Turn the ignition back on, do not start the car (Leave your foot off the brake) As soon as you see everything light up, press and hold the trip reset knob and do a long 12 second count.
4) Keep your finger on the trip reset knob. Fasten your seat belt, as soon as you fasten your seat belt, you should see the ODO display go from XXXX miles to "b-on". At that time take your finger off the trip reset knob and press it again. It should cycle to "b-off". You should be all set, turn the ignition off and unfasten your seat belt.
