Retrofitting factory swivel towbar - wiring/coding issues - what is the blue plug for?!

[Adman]

Hi all,

I've retrofitted a factory swivel towbar from another A6 (pre facelift car same as mine). Mechanically it works fine. Couple of issues though related to wiring and electics. The control module has 3 sockets, the black plug from the towbar electrics, the red plug from the car and also a blue plug. I have the black plug and the red plug but no blue plug...

So far, VCDS is not picking up the trailer control module even though I have enabled it in the CAN gateway.

Couple of questions... Firstly, does anyone know what the blue plug is for? It has three wires, does anyone know where they go to? Secondly, does anyone know where I could get wiring diagrams for the control module (4G8 907 383) or harness

If i can figure what the blue plug is for, I can then hopefully work out if the control is borked and is the reason why VCDS is not picking it up.

If anyone has experience with this, I'd appreciate your advice. I know Kufatec do a loom with the blue plug but its 140 quid - for a loom. I want to avoid that if possible.

Thanks in advance

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[Adman]

Just saw this post... (which annoyingly did not come up on my searches earlier)

Question C7 Avant dedicated towing wiring

I'll check in the morning now, but hopefully i'll find the blue plug somewhere over the wheel arch...

[Adman]

So I found a small two wire connector which i connected and the controller is now visible. I've coded the trailer module and recoded all of the other modules, (engine, ABS, Parking and camera) but lights on the trailer aren't working - not a single one. I would have thought i would have at least something working. It must have something to do with this blue plug!

I've got one fault on the can gateway now - 0021 control, module incorrectly coded (U1014). Just need to figure out which module which I'll do later.

Any help would be much appreciated

[Adman]

So thought I would update this thread so it can now be closed off. Hopefully the following will be of use to anyone else undertaking this retrofit.

A few things I have found out...
After looking at Elsawin the blue plug turned out to power the led on the towbar release lever. The three wires ensure the LED is red if it is locked in either position. However this didn't get the electrics working on the trailer. This turned out to be two pins needed swapping in the t17t towbar plug in the spare wheel compartment. Pins 16 and 15 needed swapping but as they are different sizes, i had to cut and solder the wires. Hope this helps someone else out as it took me a good few hours to diagnose this.

Everything works as it should now.

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[dtwort]

Hi Adman,

Are you able to post your coding of your towbar module?

Thanks

Darren

So thought I would update this thread so it can now be closed off. Hopefully the following will be of use to anyone else undertaking this retrofit.

A few things I have found out...
After looking at Elsawin the blue plug turned out to power the led on the towbar release lever. The three wires ensure the LED is red if it is locked in either position. However this didn't get the electrics working on the trailer. This turned out to be two pins needed swapping in the t17t towbar plug in the spare wheel compartment. Pins 16 and 15 needed swapping but as they are different sizes, i had to cut and solder the wires. Hope this helps someone else out as it took me a good few hours to diagnose this.

Everything works as it should now.

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[Adman]

Hi Darren,

Coding for the towbar module as below..

Address 69: Trailer (J345) Labels:. 4G8-907-383-V1.clb
Part No SW: 4G8 907 383 HW: 4G8 907 383
Component: Anhaenger H07 0100
Revision: 5G001002 Serial number: 00000123116274
Coding: 0109080000000000
Shop #: WSC 02391 785 00200
VCID: 71EFEBA4A82096CE6E-8024

Cheers

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