C4 GP MK2 Canbus fault

[Duffy3074]

Evening
I’m chasing a fault in the windows on my 2017 C4 Grand Picasso
The drivers window works but the other three are dead, the nearside mirror doesn’t fold or adjust either
I suspect a canbus fault, probably in the drivers door loom
Before I get stuck in, does anybody have a wiring distance for this?
Thanks!

[mickthemaverick]

Sorry to say your car is younger than my backup system information which only goes up to 2012 cars so I cannot help.

[Duffy3074]

Loom off this morning, you can do this without removing the door but it is tight
One wire (pink) completely broken and 4 others with broken insulation and corrosion not far behind
A replacement loom is north of £200 nowadays so soldering iron was deployed!

[RichardW]

A good find. How many miles? I saw from scanning ours that it is reporting an intermittent mirror heating fault, so I wonder if there is a broken / breaking wire in there, or in the mirror housing....

[Duffy3074]

98k, somebody has had a half hearted go at accessing the loom before but has given up, I suspect it may well be a long term issue

[Duffy3074]

Loom back in and full function restored!
If you’re going to do this without removing the door, remove the door card, exterior handle and the bolts for the door lock, this will allow you to access the connectors for the keyless and the lock itself, remove the speaker, cut all of the retaining ziplocks (you can re use the base so don’t just yank them out) and you can feed all of the door loom through the hole in the door towards the shell
Inside the car remove the plastic sill trim (it just pulls up) and the lower dash trim (it pulls straight back) this gives you access to the two Torx screws that hold the kick panel and that then pulls off
This all gives you access to the rear of the wiring connector to the door from the shell side, you can then reach in with your hand or use a flat blade screwdriver to work the retaining lugs that hold the loom into the shell, this will come free and allow you to pull the loom and the shell side connectors into the door gap and disconnect the two connectors that are there
I put the loom onto my workbench and used a multimeter to check all of the connectors at the shell/door joint to all of the connectors that are inside the door
I did this twice for peace of mind!

[mickthemaverick]

Well done Duffy and hopefully your description will help others in due course

[Duffy3074]

Meant to add that soldering the cables can be a pig, especially if they've corroded. Strip the insulation back and use some fine wire wool to give the metal a clean beforehand will solve that