A presence detection sensor for unlocking an opening panel of a motor vehicle, said sensor comprising a microcontroller implementing an analog-digital converter and comprising a first input, a second input forming the voltage reference of said analog-digital converter, a third input for supplying the microcontroller with voltage, and a plurality of inputs-outputs, and a capacitive voltage divider connected to at least one of the inputs-outputs of the plurality of inputs-outputs. The sensor comprises a resistive module connected between the first input and the second input of the microcontroller and a capacitive module connected between the second input of the microcontroller and a ground.