If your vehicle is showing seatbelt warning chime keeps dinging even when buckled, here are the most likely causes and the parts you'll need to fix each one.
The microswitch inside the buckle that detects the latch is prone to failure from daily wear, spilled drinks, or accumulated debris. When it fails, the vehicle's computer doesn't register that the metal tongue has been inserted.
A heavy bag, laptop, or pet placed on the passenger seat can trigger the weight sensor, making the car think an unbuckled passenger is present. Alternatively, the sensor pad inside the seat cushion may have failed.
The wiring harness connectors under the seat can be accidentally unplugged during deep interior detailing, stereo installation, or snagged and broken by moving the seat back and forth.
The main computer responsible for interior electronics and warning chimes is misinterpreting the seatbelt sensor signals due to a software glitch or internal hardware failure.