Trailer cable ??

[Mal9876]

Hi to all and happy new year
Having trouble with parking assistance fault on c4 auto grand Picasso 2012 have tried the fuses but having no luck I did have a tow bar fitted and noticed recently when I hooked up the trailer the lights didn’t work checked the fuses inside the glove box and found this anyone know what it’s for and where does it plug in too
Regards mal

[GiveMeABreak]

Looks like someone has been there before and spliced into one of the wires (never a good idea on modern vehicle electronics).

It's important that you have the correct compatible wiring loom for a trailer / towing. Genuine Citroen ones have their own fuse units designed for the vehicle's electronic systems and proper fitting kits to ensure full compatibility with the vehicle's ESP and parking assistance systems for example.

[PaulC5]

What is behind the tape on the yellow wire ? Possibly this is the connection taken to the tow bar wiring. You need to look in the back/boot area to see if the tow bar wiring has a relay from this black wire and then check if the fuse on the black wire is ok - usually a blue 15 amp if just for tow bar lighting and not a caravan. There might also be a wiring problem in the relay area. If the black wire is not connected to the yellow one then maybe the spade on the black wire has just dropped out of a spare position in the yellow part of the fuse box.