When this little Smart ForTwo was booked in for rear parking sensors, I laughed!

However, when Darren reversed it into the workshop to get the colour coded sensors, he did comment on the fact that seeing out the back of this little thing was in fact tricky. It was difficult to gauge the distance so we got down to fixing that.

When installing aftermarket parking sensors, it’s important to check the specifications of your selected parking sensor kit.

The Steelmate parking sensors need to be installed at a minimum height of 45cm and a maximum of 65cm for best results.

Most other companies put the sensors in the black part at the bottom of the bumper, however, the maximum height we could achieve here would be 40cm, this is important as installing the sensors at this height would increase the chances of false warnings and generally low performance.

It’s understandable why this compromise is made though as it’s quite a big job to install the sensors at a more optimal height on these cars. However, we decided the extra work would be worthwhile, we removed the bumper and found the best place to mount the sensors at an ideal height of 60cm meaning we could use the maximum sensitivity setting on the control box with no adverse effect. 

For more information see our range of sensors or contact us for help 01368 860800




1. How do parking sensors work?

Reverse parking sensors emit ultrasonic waves that bounce off objects behind the vehicle. The returning wave from these ultrasonic proximity detectors is sent to the control box which calculates object distances from the vehicle. This warns the driver with acoustic tones which increase frequency indicating the distance until a steady tone means stop. Some systems may also include visual aids, such as LED or LCD readouts to indicate object distance.

2. Do tow bars affect parking sensors?

The simple answer is yes however some parking sensors are able to be adjusted to not see obstruction’s like tow bars and rear-mounted spare wheels. Check the spec before purchase or raise a support request.

3. How much are parking sensors?

Like everything else there are cheap and quality products and you can get inexpensive sensors which look like good value but prove to be troublesome so how do you decide?

A reputable brand like MetasystemParksafe, Cobra, Steelmate, C-KO fitted will be from £99 to £240 or simply supplied for less than £50 depending on type and vehicle.

4. How to fit parking sensors

For DIY enthusiasts there are many online resources to aid with fitting parking sensors. We have created videos too, check out our YouTube Channel.

The essential things to remember is not to fit them too low down or pointing down.

Before drilling the bumper, check that there is clearance behind to accommodate the sensors, which will require approximately 30mm of depth before you reach any steel work on the car. Sometimes it is easier to remove the rear bumper and if you do you may find the parking sensor positions already marked on the rear of the bumper (for factory option).

Once you have decided on the location for your sensors we would recommend applying some masking tape which will also hold the drill bit steady and protect the paintwork in case you slip. When drilling, don't push too hard, leave the drill bit to do the hard work.

Bring the cabling into the car via the grommet in the boot floor and fit the sensor heads in the correct orientation (as per the instructions that come with them). Some sensors are numbered and need to be fitted in the correct sequence and orientation to work properly. The power for the control box can be made at the rear lamp cluster where all that is needed is a 12-volt positive (ignition on) and good earth and the reverse lamp 12 volts when in reverse.

Some vehicles with pulse width modulated wiring systems can interfere with certain sensors so check specification first.

5. How to clean parking sensors

Sometimes dirty sensor heads can cause false readings or even constant sound like you are right up against an obstacle. This is caused by metallic or conductive material in the small groove shorting out the ultrasonic transponder. Usually washing with a soapy sponge clears it but sometimes a short blast from a pressure washer (not too close) does the trick. Do not be tempted to scratch about with a screwdriver or anything sharp, you may damage them permanently.

6. Do I need front parking sensors, how do front parking sensors work?

Front parking sensors are nice to have and give added comfort to parking your car. They can be operated in two ways. You can have a simple switch on the dash, turning them on or off when required, or fully automatic. The automatic types have an added control box which senses when the vehicle is travelling slowly and turns on the front sensors.

7. How to paint parking sensors

We offer painted sensors to exactly match the colour code of your car. If you are going to try to paint them yourself you should be aware that proper preparation is essential and too much paint kills sensor heads. Light rubbing with fine paper to prepare the surface then a light application of flat undercoat then when dry a misting of colour repeated until completely coloured but not too thick then a final thin coat of clear lacquer to finish. Much easier to simply let us supply the kit pre-painted for you :-)

8. How to test parking sensors

If you suspect your sensors are not functioning properly you can switch them on and individually get very close to each sensor and you should be able to hear a very faint ticking noise from all good sensor heads. The dead one will be the one that is silent.

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