Why do my OEM S4 xenon LED DRLs flicker after swapping from halogens?

I’ve got a 2009 B8 A4 that originally had halogens. I swapped in OEM S4 bi-xenon headlights with the 10-to-14 pin adapters. Ballasts and bulbs are good.

Low beams work perfectly.

High beams work.

But the LED DRL strip flickers (like cold diagnosis pulsing). And sometimes the high beams flicker as well, I have not installs them yet but I tested them.

It flickers with ignition on and while running. The xenon itself is stable — just the LED strip.

I’m about to get OBDeleven (PRO) to code it properly but before I spend $200 I wanted to see if anyone could slide some information, from what I’ve read it sounds like:

Need to disable cold diagnosis

Possibly adjust Byte 18 lighting config

Enable bi-xenon shutter coding

Has anyone here done this exact retrofit on a halogen car? What Byte 18 value did you end up using?

Appreciate any help before I start

Posted Feb 25, 2026, 9:09 PM UTC

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