Back warning buzzer system for vehicle having trailer mounted thereto

A back warning method for an automotive vehicle having a trailer mounted thereto, comprising the steps of:

• (a) starting vehicle's engine;
• (b) when at least two sensors selected from a plurality of sensors equidistantly mounted to the back bumper of the vehicle detect a rear object with the transmission in “P” or “N” position and a distance between the vehicle and the rear object is within a predetermined range, allowing a control unit to determine that the trailer is towed behind the vehicle so as to control the selected sensors to be turned on and a buzzer to be turned off after the lapse of three seconds;
• (c) when the selected sensors detect the rear object with the transmission in “P” or “N” position and the distance between the vehicle and the rear object is beyond the predetermined range, allowing the control unit to determine that the rear object is a general obstacle so as to control all of the plurality of sensors to be turned on and the buzzer to be turned on;
• (d) when the vehicle is stopped with the transmission in “R” position for a sufficient time period, allowing the control unit to control the selected sensors to be turned on and the buzzer to be turned off;
• and
• (e) when the vehicle is operated during the stop of the vehicle with the transmission in “R” position for a sufficient time period, allowing the control unit to control all of the plurality of sensors to be turned on and the buzzer to be turned on.