A method for acquiring signals such as signals representative of the state of contacts (C1-Cn) of a motor vehicle, on communication ports (P1-Pn), which can be configured either in input mode or in output mode, of an electronic unit (1), called a computer, of the motor vehicle, according to which method the signals are acquired periodically by the alternation of time intervals of acquisition of the signals with standby time intervals. This method consists in configuring each communication port (P1-Pn) in input mode during the acquisition time intervals, and in level 0 output mode during the standby time intervals.