Originally posted by mythik
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If you look closer at your picture of the VCDS screen above, you will notice that your highlighted piece of the code-string for the BCM is the 5th & 6th digit from the LHS. This means that you have highlighted Byte 2 (remembering that the extreme left-hand-side pair of digits in your picture is Byte 0).
So, according to your instructions, your original Byte 2 value was hex1C, which has the equivalent binary value 0001 1100. And, you have changed the value of this byte to hex1D, which has the equivalent binary value 0001 1101. This means that you have altered Bits 0 and Bit 1 in Byte 2 (remember that in binary, the extreme RHS digit is Bit 0 and the extreme LHS digit is Bit 7)
Specifically, the change that you have made to Byte 2 is this:
- Original Bits 0-1 = hex0
- New Bits 0-1 = hex1
The Long coding Helper screen for Bits 0, Bit 1 on Byte 2 looks like this:

Translating the options into English yields this:
- hex0 =Halogen
- hex1=Halogen_main_beam_assist
- hex2=Xenon_AFS
- hex3=Xenon_AFS_and_main_beam_assist
- hex4=Bi-xenon_AFS
- hex5=Bi-xenon_AFS_and_main_beam_assist
- hex6=Bi-xenon_AFS_and_MDF_GLW
AFS, (Advanced Frontlighting System)-dynamic cornering light (via the cornering light CAN bus)
FLA (Main beam assist) Assistance system which supports the driver when changing from main beam to low beam headlights, in order to prevent dazzling other road users
hence -why your tweak works!!
Don
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