Trailer electics - faulty Trailer prep [Resolved]

[Willam]

Thinking about the parking light functionality, I just went out and tested this.
Everything switched off, then move turn indicator stalk up (right turn) - this switches on the van and trailer right hand side lights (as parking lights), as expected.
Now, repeat above, but with indicator stalk down (left turn). - this switches on the van left hand side lights (as expected), but also the trailer right hand side light (unexpected, assuming trailer lights are designed to mimic that of the vehicle).

 

[n10n]

I have just fitted a Westfalia towbar and 7 pin Trailer Prep. electrics (from PF Jones) to my 2019 T6 Transporter.

I did not get any coding instructions with the towbar. I think the van must have been coded when VW fitted the Trailer Prep at the factory because, when the 7 pin plug is connected, the van responds as expected (trailer icon shown on dash, parking sensors disabled etc).

Ah ok I misread the trailer electrics was installed now as well.

have found nothing that indicates the possibility of coding one side light independent of the other, however, I guess this might be applicable for when one of the side lights is used as a parking light, controlled by the turn indicator?

Both sides should behave exactly the same. So even if there would be some indicator magics you should be able to verify the functionality by testing the other side with indicators.

Aus coding is the unknown factor here. a) You don't currently have a way of reading the current coding and b) If you choose to try the new module route you will most likely need a way to code it - unless sourcing a second hand unit and it happens to have correct coding already. Considering this, I would start by getting either VCDS or OBD11 and see about the country coding first. If you intend to keep the van for some years it will pay itself back very soon.

 

[n10n]

Thinking about the parking light functionality, I just went out and tested this.
Everything switched off, then move turn indicator stalk up (right turn) - this switches on the van and trailer right hand side lights (as parking lights), as expected.
Now, repeat above, but with indicator stalk down (left turn). - this switches on the van left hand side lights (as expected), but also the trailer right hand side light (unexpected, assuming trailer lights are designed to mimic that of the vehicle).

This might actually be indicative of the Aus coding? We (Finland) did not have side light functionality until quite recently. They were called parking lights and always lit on all four corners - if the trailer module follows similar convention it might put both sides on always but the left one just doesn't work.

Found this remark from Tasmanian gov guide for light trailer inspections:




=> I read that as small trailers don't need side lights, so they might be not connected. But large trailers do and then they must be lit on both sides.

 

[Willam]

Ah ok I misread the trailer electrics was installed now as well.



Both sides should behave exactly the same. So even if there would be some indicator magics you should be able to verify the functionality by testing the other side with indicators.

Aus coding is the unknown factor here. a) You don't currently have a way of reading the current coding and b) If you choose to try the new module route you will most likely need a way to code it - unless sourcing a second hand unit and it happens to have correct coding already. Considering this, I would start by getting either VCDS or OBD11 and see about the country coding first. If you intend to keep the van for some years it will pay itself back very soon.

Good advice - I will be keeping the van a long time so getting a VCDS or OBD11 device is what I need to do. Thank you.

 

[Willam]

Although not likely to be coding issue but what's the current coding?

What does the controller itself think about missing lights? Does it "see" them as active?
OBDeleven > Control units > 69-Trailer control > Live data > Channel 4

• Value 1 = left turn signal
• Value 2 = right turn signal
• Value 3 = left tail light
• Value 4 = right

Please post what's in channel 9? Values 1 - 4?

EDIT: Apologies, I somehow thought you had OBDeleven at hand.

Will post values when I get VCDS or OBD11, which is what I need to do next! Thanks for helping.

 

[n10n]

Good advice - I will be keeping the van a long time so getting a VCDS or OBD11 device is what I need to do. Thank you.

Quick primer on VCDS vs OBD11:

* VCDS is more expensive to acquire but is a one time cost. VCDS does both coding and diagnostic data view / collection, pretty much the best tool available for these purposes. Needs a windows laptop. Don’t be tempted by the wifi version, not worth it.

* OBD11 is cheaper to acquire but requires subscription so costs accumulate over the years. Does coding reasonably well but lacks severly on diagnostic data view / collection. Phone app only - is very convenient to keep always with you on the road.

So… both are good tools, little bit different focus, strengths and weaknesses.

 

[Willam]

Update on this issue:
Headline: Fixed today by correcting coding. All hardware, including Trailer Module and wiring was OK.
Details to follow shortly, for the record and in case it helps anyone else working in this area.

 

[Willam]

Reminder of the fault: Trailer left hand tail light not working (all other trailer lights OK).
Details of fix:
Bought Ross-Tech VCDS from Gendan yesterday afternoon. It arrived this morning!
Installed the software (on a 12 year old Windows 8 PC). No problems.
Full autoscan. A few old faults revealed and cleared but nothing relevant.

7 pin trailer socket connected to van.
Select Control Module>Electronics 1>69-Trailer
Select Output Tests
Select Trailer Tail Light Right (M61)
This ran successfully and switched on the right trailer light. Good, as expected as this light was not a problem.
Selected Trailer Tail Light Left (M60)
This did not run and did not switch on the left trailer light. Error message 'This output is not supported by control module'

At this point, it looked as if the Trailer Module had a fault, but it made sense to go on to check the two Country codes;

Select Control Module>Installed>17-Instuments.
Country code was set to 'Rest of World'
Changed this to GB (with soft reset)
Re-checked trailer lights using Output Tests, as above - no change; LH trailer light still not working.

Select Control Module>Electronics 1>69-Trailer
Country code was set to 'Australia'
Changed this to 'Rest of World' (very limited options - North America, Australia or Rest of World (GB not an option)

Re-checked trailer lights using Output Tests, as above - This ran successfully for both LH and RH trailer lights.
Turned on side lights using van light switch - both LH and RH trailer tail lights now working.
Fault fixed; thanks to all Forum members who have helped with comments an essential advice in previous posts.