I had a guy do my install and learned a heck of a lot! But, I went from halogen to the LED xenons. I have the midline CECM(2012 TDI) that came with the car. And all my light functionality works, high beam, LEDs, and We didn’t have to run trigger wire, as most people with halogens do.
I purchased the lights and CECM from a guy with a wrecked 2012 GTI, thinking I Also needed the CECM. I found out it was the same midline CECM, and so I didn’t have to swap out. I checked the software revision# with OBDELEVEN, and my midline is 657. They said you need software revision of higher than 525(can’t remember the number...
Anyhow, just check if you have the 14pin(halogens were 10pin) plugs for the headlights, which I’m assuming you would? You’ll definitely need VCDS or OBDELEVEN to activate the correct parameters for the lights. The coding parameters that I had to enable the Oem bixenons w LED DRLs, are below, as an FYI. The only parameter you should be careful, is Byte 18. I didn’t have an issue changing mine, but I heard VW masked some CECM byte 18 parameters, and showed up as “00” So when they went to try different codes for the retrofit, other functionality of their lights didn’t work, and/or bulb out errors. You only change byte 18 if swapping to LED rear lights, or the front headlights to bi-xenons. I had to change, and I’m guessing you might have to as well, but just make a backup (obdeleven /VCDS functionality) as you can always revert back.
If you do a search for the xenon LED coding, you can find out what other GTI owners, as there’s a few common ones that work. I’ll send the list that I found, if I can dig it up.
Byte 9 - Manual activation/deactivation for DRL suppressed = Active-checked
Byte 11 - DRLs /Active-checked
-Permanent Running light via low beam = unchecked
Byte 14 - Bi-xenons with shutter installed =Active-checked
Byte 15 - DRLs with separate lights = Active-checked
-DRLs adaption MFA+ = Active-checked
Byte 17 - Bixenon additional high beam (installed) = checked
Byte 18 - hex=41
Byte 24 - Hex =E4
Byte 25 - DRL LED brightness =Full
-High beam via shutter Installed =checked/active
Byte 26 - DRL only with assistance driving light =unchecked
Byte 27- LED DRL module for parking light and DRL =Installed/checked
Cheers,
Ron