Rear parking sensor doesn't work

[powysjune]

Can anyone advise on how to remove the rear bumper to check if there is a broken wire to the rear parking sensor? The front sensor works ok but the rear one has never worked since we bought the Cali earlier this year (2005 left hand drive model).
Thanks
June

 

[smgcowfoldparts]

Do you have a towbar fitted?

 

[teeboy]

Do you mean one sensor doesn't work (i.e. you get 3 areas covered with a dead spot)

Or no rear sensors at all work?

If you have no rear sensors it might imply bad coding, or bad towbar wiring as eluded to by SMC.

If it is only one sensor not working then it might be worth investigating the wiring and the sensors - you can get you hand to some of them from under the bumper.

Fully removing the bumper is pretty easy - rear lights out - undo some screws from the rear wheel arch, and remove some of those weird VW plug/screws from under the bumper, as described here: http://www.brick-yard.co.uk/forum/how-t ... 52710.html

To remove the VW plug/screws I screw a small self tapping screw into the core of the screw and then pull on that to remove the core - this will become obvious when you look at it

 

[smgcowfoldparts]

Main reason I have seen for rear sensors not working and the towbar question is more often than not a 13 to 7 pin adapter has been left plugged in the towbar socket and the sensors are still turned off as the van will think there is a trailer behind it.

cheers

 

[teeboy]

Yep that would do it

 

[powysjune]

Many thanks for the replies. No towbar. I should have said that the rear sensor does work occasionally which is why we think it must be a bad connection and need to take the rear bumper off to look. Thanks teeboy for the instruction link, really useful. This forum is a great resource!

 

[HistoryBob]

Main reason I have seen for rear sensors not working and the towbar question is more often than not a 13 to 7 pin adapter has been left plugged in the towbar socket and the sensors are still turned off as the van will think there is a trailer behind it.

cheers

Alex. Should the rear sensors turn off automatically when a trailer is hooked on?
Mine don't. Is it a coding issue?

 

[teeboy]

If you have pukka Westfalia wiring then it should disable the rear sensors - and this is enabled by coding.

It is possible to just splice wiring into the rear lights, and if this is done with a bypass rely it is a totally valid way of installing, however you will loose the ability to disable the parking sensors (any your parking sensor display will not show a trailer)

If you are towing big heavy things I would go with the pukka westfalia wiring as it also adjusts the abs and stability control - but if you are only towing light trailers or bike racks then it shouldn't be a problem...

Who fitted the tow bar - if it was a VW one then it should be code-able.

T

 

[HistoryBob]

If you have pukka Westfalia wiring then it should disable the rear sensors - and this is enabled by coding.

It is possible to just splice wiring into the rear lights, and if this is done with a bypass rely it is a totally valid way of installing, however you will loose the ability to disable the parking sensors (any your parking sensor display will not show a trailer)

If you are towing big heavy things I would go with the pukka westfalia wiring as it also adjusts the abs and stability control - but if you are only towing light trailers or bike racks then it shouldn't be a problem...

Who fitted the tow bar - if it was a VW one then it should be code-able.

T

The tow bar was fitted by 'TowBars2you' of Carlisle. I insisted on genuine Westfalian tow bar and wiring harness. However, the job has been an absolute nightmare. I spent three days waiting around in Carlisle whilst they struggled with it. The fitter had to use another company (Indespension) to do the electrics and this was where the delay occurred. They first said the modul was wrong and and then that the harness was faulty.
When I got the van back the auxiliary heater wasn't working and the rear sensors were no longer attached to the bumper. I've managed to get the heater going and have stuck the sensors in myself. Now I find that they should switch off when the trailer or bike rack are attached which they don't. Is this a simple coding job?
I haven't paid for this job yet and the guy is chasing for payment which I'm not inclined to do. If the rear sensors should switch off then it might cost me to take it in to have it looked at. I'm not a happy bunny.

 

[WelshGas]

Yes. VW fitted tow bar then rear parking sensors are disabled when trailer electrics connected to tow bar socket. Reversing camera is not disabled.
So, if the tow bar has been fitted using the correct harness etc: then the last stage should have been coding the vehicle electronics. Something that they probably didn't even know about.

 

[smgcowfoldparts]

Main reason I have seen for rear sensors not working and the towbar question is more often than not a 13 to 7 pin adapter has been left plugged in the towbar socket and the sensors are still turned off as the van will think there is a trailer behind it.

cheers

Alex. Should the rear sensors turn off automatically when a trailer is hooked on?
Mine don't. Is it a coding issue?

Absolutely, the van needs to be coded to tell it that it now has a towbar as it interacts with ABS, ESP etc...

When a trailer is hooked up then the parking sensor display on your radio will display a picture of a trailer behind it as well and the rear sensors don't work.

cheers

 

[HistoryBob]

Thanks Alex and Welshgas
I'm off to France for 4 weeks this morning so I'll have to wait till I get back. Guess this guy will have to wait a little bit longer for his money.
This is the first time I've used a none VW agent for work on my van. Seemed like a bargain at the time. Caveat emptor.

 

[Stu]

I think we discussed this at the time you had the problems and I said to you then that I don't think they were doing a proper job.

Did you find a towing control unit under the front passenger seat like I said?

 

[Stu]

June,

Rather than go to the trouble of removing the bumper and blindly looking for a broken or damaged wire a diagnostic check would establish the fault for you.

Normally if there is a faulty sensor you will get a multi tone beep to alert you of a fault when selecting reverse.

Diagnostics such as VCDS (which some members here have) can pin point the fault down to a sensor and also invoke a test.

 

[Geanina]

Hello, can anyone tell me how i can enable the parking senzor. I gave my t6 to my brother and don t know how he turned it off! Tnks.

 

[Andy]

Switch on the dash ?

Sent from my SM-G900F using Tapatalk

 

[larsmars]

I have a left and right rear parking sensors that aren't working(no clicking sound). the garage connected the van to the Computer and told me these defect. How can I remove and replace these? And eventually check the faulty sensor if it is really faulty or the problem is something else.

 

[WelshGas]

I have a left and right rear parking sensors that aren't working(no clicking sound). the garage connected the van to the Computer and told me these defect. How can I remove and replace these? And eventually check the faulty sensor if it is really faulty or the problem is something else.

They push out from behind. Each sensor has a wiring plug/socket behind bumper. Little hands might work , otherwise bumper off.
Check plug/socket is clean before replacing, not an uncommon cause.

 

[andyinluton]

Have you got an adapter for a 13 pin towing socket plugged in? that disables the rear sensors.

Do you have a front sensor that you can swap with the rear to check?