I replaced one of the parking sensors on the back of my 2007 Skoda Octavia 2 Scout.  There are several posts on this forum with partial information about the job; here is the full story.  Other models may differ, in particular access to the inside of the bumper may be different.

 

Symptoms: When engaging reverse gear, there is a long beep (about 3 seconds) to warn you that the sensors are not working; the outline of the car does not appear in the central display; and there are no warning tones when you reverse towards an obstacle.

 

Cause: One (or more) of the four little circular sensors on the back bumper has failed.

 

Solution: Replace the relevant sensor.

 

Time: About half an hour.

 

Difficulty:  Straightforward, but fiddly.

 

Identify the faulty sensor(s):  In operation, the sensors emit a VERY QUIET rapid ticking noise.  To hear it, find a quiet place away from traffic, and switch off the engine.  Switch on the ignition, and engage reverse gear.  Kneel down by the back bumper and put your best ear hard up against a sensor.  Even when you press your ear hard against the sensor it may be a few seconds before you hear the ticking; it is VERY QUIET.  Repeat, until you find the one (or more) that is not ticking.  That is the faulty one.  In my case, it was the inner right (photo).  Switch off the ignition, and put the keys in your pocket to make sure nobody starts the engine while you are underneath the car.

 

Replacement part(s):  Ebay of course, cost £12.49 including postage.  There are many versions, I bought mine from West Midlands Car Parts, www.westmidlandscarparts.co.uk, 07779 950159. No particular recommendation, but it was very cheap, it arrived quickly, it fitted, and it worked.  Check carefully on the application list that you have the correct one for your car.

 

Look closely at the part when you get it: you will see that there is one raised tab on the cable connector socket, which clicks onto the fitting on the end of the cable; and there are two raised tabs on either side of the main body of the sensor, which click onto the permanent fitting which stays attached to the inside of the bumper.  Remember the positions of those raised tabs (circled in the photos).

 

Tools required: A torch to illuminate the inside of the bumper (I used a head torch, but not on my head.  One of those magnetic non-directional LED light arrays that you can get from Wilko's would have been better); and a tiny screwdriver (photo), to lift the plastic catch that clicks the cable connector onto the sensor.

 

Detach the faulty sensor from the inside of the bumper:  On my car there is a rectangular aperture under the middle of the back bumper (photos) that you can get the torch, one hand and your screwdriver into.  All the internal work is done with one hand.  Lie on the ground under the bumper, and reach in with one hand.  Using your fingernail or thumbnail, lift one of the plastic tabs which holds the body of the sensor to the bumper fitting, while using your other hand to GENTLY push the sensor inwards from outside.  When the first clip is free (surprisingly quick and easy) continue to press inwards gently from outside to prevent it clicking back into place, and use your thumbnail or fingernail to lift the tab on the other side of the sensor body.  The sensor will come free from its mounting and dangle on the cable.

 

Detach the faulty sensor from the cable:  Inspect the dangling sensor in the torchlight, and note that the catch on the cable side of the connector socket lies flat against the body of the sensor, so you have to use a very small screwdriver to get under the catch and lift it.  Doing this with one hand is tricky, but I found I could brace the sensor against a part of the bumper and push the screwdriver in.  Then you can separate the sensor and the cable with one hand.

 

Attach the new sensor to the cable:  This is easy.  Push it until it clicks.

 

Test the new sensor:  Letting the new sensor dangle, switch on the ignition and engage reverse gear.  The system should now work, with a short beep and the outline of the car appearing in the central display.  Because the sensor is inside a small space it should continue beeping to tell you that you are about to reverse into something.  Assuming all is OK, select neutral and switch off the ignition.  Put the keys in your pocket.

 

Attach the new sensor to the inside of the bumper:  Simply reach in, take hold of the sensor, turn it to its correct orientation, and push it into the fitting until it clicks.  I found it useful to shine a torch into the hole from outside so that I could see when I had the sensor roughly in the right place.

 

And you're done.

 

This worked for me.  If it doesn't work for you, perhaps (a) you have another faulty sensor, (b) you have a wiring fault, (c) you have bought the wrong replacement part, (d) there is a fuse blown, (e) the replacement part is faulty, or (f) something else.

 

Good luck, and I hope this helps.

The Ebay link for the part that fits my 2007 Scout 2.0 103 kW is https://www.ebay.co.uk/itm/262681721450.

Very useful post!

 

I now have a pretty good idea of how they are fitted. Many thanks!

I have completed mine today and followed your instructions which were fantastic and bang on with the exception of mine having a tow bar fitted so space was really limited. After much cursing,and toying with the idea of bumper removal, I eventually pushed the complete unit through with the intention of gluing back into place. The real good news was that it is held in place with two foam adhesive pads, so cleaned them up applied new pads and popped it all back together.  

Part number for sensor was 7H0919275C if you do a search it will throw plenty of hits. Thanks to the original OP.