OEM tow bar module issue (some what urgent)

[Jje939]

Hello.
And greetings to everyone.
Been searching around this forum and it seems that trailer electrics is quite a common issue. Unfortionately, none of the existing threads match my problem (or cant find it). I get no lights on trailer whats so ever and my car does not recognize that the trailer is connected. All fuses are ok (even the ones under driver seat, LHD car). When i unplug the larger connector from the module, the trailer mode is activated, but no lights work. Local VW workshop read the code and module status is ok.

Trailer is tested with a none-module T5 and it works 100%. I also tried to activate the trailer mode with direct connecting the pins with a light but no dice.

Would this be simply bad connections somewhere so that the module does not get contact or is the module simplu broken but still shows OK status?

Any tips on common connector faults are welcome, since i need to tow a boat very soon.

 

[Pauly]

Some more info would be handy, what model/year is the van ?
Is it factory fitted ?
Has it ever worked ?

 

[Jje939]

Yes. The headline says OEM so factory. 2013-2014 van 2.0 tdi 4 motion. And it has worked earlier.

 

[Robert]

OEM stands for Original Equipment Manufacturer. It refers to a company that produces components or products that are used in another company's end product.

The OEM typically manufactures parts or products based on the specifications provided by the company that will use them in their final product.

OEM term in itself doesn't define if equipment was factory fitted or retrofited at any later stage.

 

[Jje939]

Its manyfacuter by Hella and is installed by factory. Anyway, defining the term OEM did not fix my issue.

 

[n10n]

Check the powers and grounds to the socket first.

To do this, first pull a temporary wire from a battery negative close to the socket and measure, with a multimeter, you get 12v on pin 9 all the time and on pin 10 with ignition on. If that does not work you have a power feed issue to those pins.

Then repeat the same for grounds, pull a temporary wire from battery positive and check you read 12v against pins 3, 11 and 13. If not, you have a grounding issue in one or more of those pins.

Ofc the module can be broken as well but to me wiring problem sound more probable. And not sure how to test the module.

 

[Jje939]

Check the powers and grounds to the socket first.

To do this, first pull a temporary wire from a battery negative close to the socket and measure, with a multimeter, you get 12v on pin 9 all the time and on pin 10 with ignition on. If that does not work you have a power feed issue to those pins.

Then repeat the same for grounds, pull a temporary wire from battery positive and check you read 12v against pins 3, 11 and 13. If not, you have a grounding issue in one or more of those pins.

Ofc the module can be broken as well but to me wiring problem sound more probable. And not sure how to test the module.

View attachment 201194

Thank you, this took me forward alot. I did some testing before but could not make anything out of it. So all earths are ok and also pin 9 but pin 10 nothing with igniton on. So my guess is to track and see all the connections to the module (assuming its the grey wire all the way)?

 

[n10n]

Did you test pin 10 also with engine running or just ignition on? I’ll try to verify from wiring diagrams in a bit which one it should be

Don’t mind the wire colors in above diagram, that was just some generic pinout from google

Anyway, towbar is wired to left D-pillar, then on to left seat base. The ignition live will not go to the towbar module at all, fuse and relay for it are under left seat base.

 

[Jje939]

Did you test pin 10 also with engine running or just ignition on? I’ll try to verify from wiring diagrams in a bit which one it should be

Don’t mind the wire colors in above diagram, that was just some generic pinout from google

Anyway, towbar is wired to left D-pillar, then on to left seat base. The ignition live will not go to the towbar module at all, fuse and relay for it are under left seat base.

Yew thats a good point, since i just noticed that the wire colors are completly different. But one thing comes to mind and its that im using a 7pin adaptor, and the pin 9 does not seem to connect to any pins in the outlet of the adapter. The funny thing is that is has worked withe this adapter

 

[n10n]

Hmm looks like pin 10 might not be connected at all in the socket, these are T5.1 diagrams from 2010 onwards and dated 10.2014, it's definitely different to T6. And if pin 9 is not used by the 13-7 pin adaptor, neither of the live feeds has anything to do with the issue.

Then next would be checking all the relevant fuses from below diagrams and Fuse Box Diagram Volkswagen Transporter (T5.1; 2010-2015) but you mentioned checking these already so I guess then it would be either wiring to or from the towbar module or the module itself.

Edit: personally I would start by checking towbar module connector has good ground on pin 10, ignition (or engine run) live on pin 2 and permanent live on pins 9, 12 and 11. And get the vehicle scanned, towbar module has a can bus so scanning might reveal some faults.

 

[Jje939]

Hmm looks like pin 10 might not be connected at all in the socket, these are T5.1 diagrams from 2010 onwards and dated 10.2014, it's definitely different to T6. And if pin 9 is not used by the 13-7 pin adaptor, neither of the live feeds has anything to do with the issue.

Then next would be checking all the relevant fuses from below diagrams and Fuse Box Diagram Volkswagen Transporter (T5.1; 2010-2015) but you mentioned checking these already so I guess then it would be either wiring to or from the towbar module or the module itself.

Edit: personally I would start by checking towbar module connector has good ground on pin 10, ignition (or engine run) live on pin 2 and permanent live on pins 9, 12 and 11. And get the vehicle scanned, towbar module has a can bus so scanning might reveal some faults.


View attachment 201290



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View attachment 201292

The pins tested ans gave good result. There is one pin in the black connector im the module that gives out barely 4v. Guess thats thats the signal. But an update: Bought some electro cleaner and sprayed it in ever connection i could found connected to the trailer socket. Now i get the trailer mode on in reverse even if there is no trailer attached. Guess that is impovment?

 

[True Romance]

How much is a new module? Might be swapping it out? Messed about with my towbar issues for a while before changing out the module that fixed all the issues.

 

[n10n]

There is one pin in the black connector im the module that gives out barely 4v.

I have no idea about this honestly, might be good or not

Now i get the trailer mode on in reverse even if there is no trailer attached. Guess that is impovment?

Leak current through moisture of the cleaner. But yes, sounds like an improvement and to me it sounds like module might be fine and your towbar socket pins are just too corroded. Or the adapter is bad.

Found this from some Touareg forum: ”the tow module is looking for a load on either the Left Ind, Right Ind, Stop Lights or Brake Lights. Connecting a 12v halogen globe to any one of these was sufficient to have the tow module recognise it and could hear the relay operate.” - being vw the logic is probably similar

 

[n10n]

I would next try to see if the socket could be detached without breaking to get behind it. The wires might be just screwed to the terminals. If so, it would be easier to check the wire ends for corrosion and test the trailer detection directly from wires.

 

[mmi]

Not sure about T5.1 but T6 OEM trailer detection requires that in the trailer (minimum) two of the following circuits are present (having regular bulbs):
- Left parking light
- Right parking light
- Left indicator
- Right indicator

13 pin towing socket

I had a tow bar fitted at vw when I bought my t6 but it was fitted by an outside firm, I have now found that the pin no 10 (fridge ign live) is not working. Would it be ok to put a link wire from pin 9 perm live across to pin 10 , I know that if the fridge is switched on 12v and left on...

www.t6forum.com

 

[Jje939]

Update: So put a new plug on the trailer and also a new adapter. The trailer mode still stays on in reverse, but when i attach the trailer ligts work (success, i guess) So basically light work accidenttaly but now the car thinks that the trailer mode is on always when i revesre without trailer. However, i have now booked an appointent to a local vw shop.

 

[z1ts]

defining the term OEM did not fix my issue

But it helps them/us establish what you have so them/us can help you 'fix'

 

[Jje939]

So an update. The shop had a look and the wiring is ok and their diadnosis is a broken module. So apparently diagnosis tool can show "status ok" even if their not.

 

[n10n]

So an update. The shop had a look and the wiring is ok and their diadnosis is a broken module. So apparently diagnosis tool can show "status ok" even if their not.

Ok, thanks for letting us know and hope replacing the module resolves the problem!

Anyway, changing the trailer plug and adapter was a good move as the lights started to work - there definitely was an issue there as well.