If your vehicle is showing seatbelt chime sounds when placing a bag or groceries on the passenger seat, here are the most likely causes and the parts you'll need to fix each one.
Passenger seats are equipped with weight sensors to activate the airbag for adults. Heavy bags or groceries often exceed the 10-15 lb threshold, tricking the system into thinking an unbuckled passenger is present.
Many modern vehicles use capacitive occupant sensors instead of physical weight scales. Electronic devices like laptops, cell phones, or even damp items can trigger the sensor even if they weigh almost nothing.
The seat's weight sensor can lose its zero-point calibration over time, after a battery replacement, or if the seat was removed. This makes the sensor overly sensitive to very light objects.
Liquid spills, heavy kneeling on the seat cushion, or general wear and tear can damage the internal sensor mat, causing it to trigger erratically or become permanently stuck 'on'.