Originally Posted by
lush4
Hey guys i'm going around in circles.. I just purchased a 2018 GTI and want to fit the 5G2052200B tail lights . Ive been offered a set for $580 but what else do i need?
I cant work out if i need a harness and if my OBDeleven can program it.
Alot of info on fitting to a MK7 but not a 7.5 GTI.. Can any one steer me in the right direction?
Cheers, Mark
Mark - the question as to whether you need a harness, or not is determined by the number of wires in the car's loom to the rear tail lights.
Think about it - and you will realize that if there are sufficient wires in the car's loom for every separate lamp in the new tail light fittings, you will be able to control each lamp via a Leuchte-set in the BCM (because a Leuchte-set is specific to a BCM pin/socket number). If this happens, no harness is needed - typically
A harness (or, more accurately a cross-wiring-harness) is used whenever there ain't enough wires on the car's pin-connectors (from the BCM). Typically for mk7s this happens when the car is factory fitted with incandescent tail lights and the owner seeks to retrofit LED tails. LED tail light fittings have more lamps than their incandescent counterparts (like additional turn-signal lamps) - so when retrofitting these the BCM ideally needs more wires to be installed. But a harness can obviate the requirement to install more wires - what the harness does is connect together the lamps which have a common function across both sides of the car. This will free-up some of the existing wires which then can be used to control the additional lamps (I call it "wire thieving").
For example, the Brake lights on the 2 sides of a mk7 are factory fitted with separate wires back to the BCM - but really it only requires one of these wires to operate these lamps if the Brake lights are connected together and if they are operated in parallel. A harness can be used for this purpose - leaving the now unused wire to operate one of the additional turn-signal light on a retrofitted LED tail light fitting (with suitable BCM coding, of course). The same can be done to the Parking Lights - allowing the 2nd now unused wire to control the additional LED turn signal lamp on the other side of the car (again with suitable BCM coding).
Hope this all makes sense - my apology if not
Don
Last edited by DV52; 10-08-2019 at 06:31 PM.
Please don't PM to ask questions about coding, or vehicle repairs. The better place to deal with these matters is on-line, in the forum proper. That way you get the benefit of the expertise of the wider forum! Thank you.
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