Parking sensors work by ultrasound: each sensor sends out a pulse and listens for the echo from an obstacle. Once the sensor face is coated with dirt, road salt, wax residue or ice, the system starts beeping at nothing or, worse, stays silent in front of a bollard.
In Ukrainian conditions sensors get dirty fast: in winter they are caked with slush and de-icing salt, in spring and autumn with fine mud thrown up by the wheels. A regular clean takes 15-20 minutes and often clears the fault without a trip to the garage.
What you will need
Important: Do not aim a pressure washer jet at the sensors from close range and never scrape them with anything hard: the sensor membrane is thin, and a scratch or dent changes how the signal is reflected.
Step 1
Switch off the engine and parking system
Turn off the engine and remove the key or switch off the ignition. This keeps the sensors inactive while you clean and avoids false fault codes in the control unit.
Step 2
Locate every sensor
Typically there are 4 round sensors in the rear bumper and another 2-6 in the front. Some models also have side sensors at the bumper corners. Walk round the car and check each one: often only one sensor, the dirtiest, is giving false readings.
Step 3
Wash off the heavy dirt
Dampen a microfibre cloth in warm water with car shampoo and gently remove sand, salt and mud from the sensor faces and the area around them. Never rub with a dry cloth, as grit acts like sandpaper. In winter, let ice melt in a warm garage first or rinse with warm (not hot) water.
Step 4
Treat the sensors with contact cleaner
Spray WD-40 Specialist Contact Cleaner onto each sensor face and into the gap between sensor and bumper. It quickly dissolves greasy film, wax, polish residue and moisture, evaporates without residue and is safe on plastics and electronics.
Wait a few seconds, run a soft brush round the edge of the sensor, then wipe with a clean microfibre cloth.
Step 5
Check the connectors if needed
If the fault persists and you can reach the back of the bumper (through the wheel arch liner or a recess), inspect the sensor connector. Green deposits or water inside mean corrosion. Unplug it, flush the contacts with Contact Cleaner, let them dry and reconnect. The outside of the connector can be lightly treated with WD-40 Multi-Use to drive out moisture and protect against corrosion.
Step 6
Test the system
Switch on the ignition, select reverse and check how the system reacts to an obstacle: your hand, a box or the garage wall. The tone should change smoothly as you get closer, with no sudden false alarms.
Tip: Do not apply wax polish or ceramic coating to the sensors: even a thin film interferes with ultrasound. When polishing the bumper, simply mask the sensors with painter's tape.
What next
Wipe the sensors at every car wash and after driving on salted roads in winter. Treat them with contact cleaner once a season. If one sensor keeps reporting a fault after cleaning, it is probably defective and needs diagnosis. For other jobs around the car, WD-40 Multi-Use is handy for hinges, locks and battery terminals.
These uses come from the experience of WD-40 users in many countries. Always follow the instructions and warnings on the product label.
More guides in «How to use».