Here are some demo videos by smrtypants44 in a mk6 GTI. In his case he has LED taillights so yours may look slightly different.
Ross tech VCDS cable (required)
Plug the VCDS into the obd2 port and start the software. Go to Select
Select 09 - Cent. Elect. This is the central electric module (CECM)/
Click on Long coding helper. Caution: the codes and part numbers you
see here are examples only! Do not copy the numbers here! They are
for the demo cars only. Your car may have different part numbers and
equipment. Click the checkboxes and it'll change your code automatically
for your car. Take a screenshot or write down your original code before changing anything.
If you have a 2005.5-2006, go to byte 17. (may also apply to
2009). Click the checkbox for bit 0, "Emergency Brake Flash Light
active". I believe this flashes the brake lights.
If you have a 2009 or 2010 or newer, go to byte 16 and check bit 1 or 2 to turn on
emergency brake flashing via "Brake Lights" or "Turn
Signals" (hazard lights) on, depending on what you want. This is the effect shown in the videos at top.
Close the window and it will copy/paste the new code. Click Do it! to save and exit the module.
If you have more questions about VCDS mods or vag com mods on your Volkswagen Jetta, Golf, or sportwagen TDI, please ask in the myturbodiesel.com forums or search the site below: