2012 Toyota Tacoma Owners Manual - Page 829

5-2. Steps to take in an emergency * : Driver's and front passenger's seat belt buzzer: The driver's and front passenger's seat belt buzzer sounds to alert the driver and front passenger that their seat belt is not fastened. Once the engine switch is turned to the ON or START position, the buzzer sounds for 6 seconds. The buzzer sounds once if the driver's or front passenger's seat belt is unfastened when the vehicle reaches a speed of 12 mph (20 km/h). Then, if the seat belt is still unfastened after 30 seconds elapse, the buzzer will sound intermittently for approximately 10 seconds, followed by a different tone for approximately 20 more seconds.