The parking distance warning system is a parking aid that warns of the distance to obstacles behind the vehicle, and in some models in front of and behind the vehicle. An intermittent warning tone indicates to the driver how far the vehicle is from an obstacle. As the distance decreases, the repeating frequency of the warning tone rises. It first sounds when the vehicle is 1.60 metres from the obstacle. When the driver has just 20 centimetres of manoeuvring space left, a continuous tone sounds. The system operates by ultrasonic sensors mounted in the bumpers.
The sensors emit and receive pulses in the 40,000 Hz range. When a pulse hits an object, it is reflected. The sensor detects the echo. The electronic analysis system calculates the distance between the obstacle and the vehicle from the time difference between emission of the pulse and detection of its echo.
The rear parking distance warning system is switched on automatically when reverse gear is engaged.