Can you fit std LED rear-lights to a van that came with halogen without the wiring loom and does it cause any errors?
Yes you can but you need to swap the plug over (halogen has one row of 6 pins but LED uses 2 rows of 3 pins)
Halogen lights only have 5 wires connected but LED has 6 as they have an additional reverse and fog light; you can run without them or you can add the extra cable to activate the additional lights its
I’ve got the bulb warning light coming up on mine, but I think that’s probably down to it having had halogen number-plate bulbs (barn-door) before they were changed to LED.