Issue with reversing parking sensors

[8BallAddict]

Hi All,

Looking for some advise. The parking system in my S4 has recently developed a fault, I'm getting a fault code for the centre right rear sensor showing in my VCDS. I've replaced it with an brand new OEM sensor but it's still not working and a rescan is still showing the same fault. When this fault started, it didn't work for a day, then started working for a few days, then went faulty again. It did this a few times then went terminal and it hasn't worked since so I was sure it would just be a sensor issue, and the VCDS scan confirmed that. I believe there is a controller for the parking system so could it be that that's at fault? Any advise appreciated muchly. TIA!


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[gray99y]

I've mine mine two years and still got a fault. Pain in the ***. Lol

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[8BallAddict]

Really annoying as the OEM sensor wasn't cheap and I had it professionally painted before I fitted it!! Dope!


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[gray99y]

I made that same mistake too, now I'm thinking it's the control box or wiring loom.

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[8BallAddict]

Do you know if the control box being faulty can just show an fault code for just one sensor though? Would of thought it would of thrown up a separate fault code?


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[rum4mo]

I think that the parking controller is in the boot on the right hand side, if you are handy with a multimeter, you could check the wiring from each sensor plug back to the controller - just unplug the 12-way connector and check back up the rear bumper cableform. If the wiring is the same as the front sensors, pin3 on all the sensor plugs get joined together - are earth return - and connect to pin6 on the controller 12-way connector, next, pin1 on all the sensor plugs get joined together - are 12V power - and connect to pin11 on the controller 12-way connector, next, pin2 on the sensor plugs are connected to the controller 12-way connector as follows:- pin2 - output signal - left outer connected to pin5 controller connector 12-way, pin2 - output signal - left inner connected to pin3 controller connector 12-way, pin2 - output signal - right inner to pin2 controller 12-way, pin2 - output signal - right outer connected to pin4 controller 12-way.
Anyway as you can see, only 6 wires coming from the rear bumper sensors to the controller, so it should be easy to find out which wire is now missing.

Edit:- I have now checked the rear sensor wiring and have changed the numbers on the controller end connector!

Edit:- the parking controller is the one with one solid arrow on it, if only rear sensors and two solid arrows on it if front and rear sensors fitted to that car, part number 8K0 919 475* or **

 

[8BallAddict]

I think that the parking controller is in the boot on the right hand side, if you are handy with a multimeter, you could check the wiring from each sensor plug back to the controller - just unplug the 12-way connector and check back up the rear bumper cableform. If the wiring is the same as the front sensors, pin3 on all the sensor plugs get joined together - are earth return - and connect to pin1 on the controller 12-way connector, next, pin1 on all the sensor plugs get joined together - are 12V power - and connect to pin2 on the controller 12-way connector, next, pin2 on the sensor plugs are connected to the controller 12-way connector as follows:- pin2 - output signal - left outer connected to pin5 controller connector 12-way, pin2 - output signal - left inner connected to pin6 controller connector 12-way, pin2 - output signal - right inner to pin7 controller 12-way, pin2 - output signal - right outer connected to pin8 controller 12-way.
Anyway as you can see, only 6 wires coming from the rear bumper sensors to the controller, so it should be easy to find out which wire is now missing.

Edit:- the parking controller is the one with one solid arrow on it, if only rear sensors and two solid arrows on it if front and rear sensors fitted to that car, part number 8K0 919 475* or **

Thanks for all the info! I've got a multimeter so I can have a look at this. If I get some time this weekend I'll have a look this weekend. Is there an easy way to get to the cables do you know?


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[rum4mo]

Thanks for all the info! I've got a multimeter so I can have a look at this. If I get some time this weekend I'll have a look this weekend. Is there an easy way to get to the cables do you know?


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Hi, please note that I have edited my posting and changed the controller end pin numbers a bit!

Anyway, using a paperclip etc I'd expect that you could check the disconnected controller cable end connector first by looking back into that cableform and checking the impedance that you see when referencing the output of each sensor to the cable's earth return and power pins, I'd hope that you would see that one of the sensors had a vastly different reading due to either its earth return lead being duff or its supply power lead being duff. After that, you would need to remove the rear bumper, disconnect the affected sensor, confirm what you have already found from the first checks, then check to see if you can find the joining point for either the earths or power leads, cut open the cable tape and sort that issue and retape the cableform etc - good luck!

Edit:- or if you can't make sense of any readings it will be down to "point to point" testing that cableform, though I'd hope that just point to point from sensor plugs to other sensor plugs at the bumper end would, in the case of a missing earth or power connection, would be enough.

 

[8BallAddict]

Nice one, thanks again rum4mo! Looks like it's not going to be a simple diagnosis then! Fingers crossed!


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[rum4mo]

Really annoying as the OEM sensor wasn't cheap and I had it professionally painted before I fitted it!! Dope!

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Well, in preparation of me retro-fitting front sensors to my S4, I've just finished priming>base paint>lacquering 3 new sensors - 2 to use, 1 for backup or possible repair in the future! I hope that you did not bin the "used" sensor?

Edit:- 2 of my new sensors were £12 each delivered from an exSEAT dealership selling off stock, the third one was about £34, which is still way below dealer prices.

 

[gray99y]

Whoa too confusing for me, but thanks anyway

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[8BallAddict]

Well, in preparation of me retro-fitting front sensors to my S4, I've just finished priming>base paint>lacquering 3 new sensors - 2 to use, 1 for backup or possible repair in the future! I hope that you did not bin the "used" sensor?

You know what, that's a very good point! At least I have a spare now! It's in my garage somewhere.


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[rum4mo]

Whoa too confusing for me, but thanks anyway

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Well like most things, using a computer keyboard to give support is not hard, but in this case, the cableform run is quite short so should be manageable/possible.