What is a Parking Sensor?
Ultrasonic sensors in your bumpers that beep faster as you near an obstacle.
Simplified animation — not to scale.
In plain English
Small piezoelectric ultrasonic transducers fitted in the front and/or rear bumpers that emit a short pulse of inaudible sound and listen for the echo bouncing back.
"Bats and dolphins use the same trick — shout and listen for the echo — but in your bumper."
How it works
Each sensor sends out a 40 kHz "ping" several times a second and times how long the echo takes to return. Distance equals time multiplied by the speed of sound, divided by two. A control module gathers readings from every sensor and works out how close the nearest object is, then drives the dashboard speaker (or a 360° display) so the beep tempo rises and turns continuous within roughly 30 cm. Heavy rain, snow, mud or a steep gradient can confuse them.
Signs of trouble
- ⚠Continuous beep with no obstacle present
- ⚠One zone reports nothing
- ⚠Visible damage or paint mismatch around a sensor
- ⚠"Park assist unavailable" message on the dash
£45–£150 per sensor
Always get a written quote. Prices vary by car, region, and parts brand.