That's ok, 'Parking Space Gap Measurement' is what we call it
Ok, so I have undertaken a comparison for you:
You have: Rear Tailgate Harness (2): with marking MARKING 9686035180 or 9686035280 (Part number: 6534SX)
You need Harness: Part: 9800224080
You have: TAILGATE HARNESS: MARKING 9686035380 (Part number: 6534SY)
Needs: No change needed.
You have: Interior Wiring Harness (1): (Part 1609733180)
You need: Intermediate Wiring Harness (Part: 1608886880) This part is no longer available new from Citroen.
You have: Fascia Panel Harness: (Part 9802608680)
Needs: No change needed.
So you would need 2 different harnesses the large interior one from rear to front, and one in the tailgate section.
So my advice to you would be to have an aftermarket one fitted and wired up to a dimming mirror like this one did:
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