Alltrack VCDS Coding for Rear Fog Lights: A Comprehensive Guide

Adding rear fog lights to your Volkswagen Alltrack significantly improves visibility in adverse weather conditions. This guide provides a step-by-step walkthrough for enabling rear fog lights on your Alltrack using VCDS (Vag-Com Diagnostic System) coding. This modification utilizes the existing driver-side reverse light as a rear fog light and, with proper wiring, retains both reverse lights.

Understanding the Modification

This process involves modifying the vehicle’s coding to recognize and activate the rear fog light function. We’ll essentially instruct the car’s computer (BCM – Body Control Module) to utilize the driver-side reverse light as the rear fog light. By jumping the passenger reverse light to the driver side, we can maintain functionality of both reverse lights. This modification requires specific tools, VCDS software, and careful attention to detail.

Tools and Materials

Before starting, gather the necessary tools and materials:

• Plastic trim removal tool
• 8mm socket and ratchet (small extension recommended)
• T20 Torx driver
• Dremel with appropriate attachments
• VCDS Diagnostic Cable and Software

Optional Wiring Harness Components:

If you opt to create your own wiring harnesses:

• 5K0-972-705: Male T5 connector (x2)
• 5G0-972-715: Female T5 connector (x2)
• N-107-244-02: 7440 Halogen Bulb (x1 or x2)
• N-103-360-05: Male Pin Terminal (x6)
• A-018-545-872-6: Female Pin Terminal (x8)

Alternative Wiring Options (if necessary):

• 000-979-025-FA: Repair Wire (x4) – Alternative for female pin terminals
• 000-979-020-E: Repair Wire (x3) – Alternative for male pin terminals if you lack a Molex crimp tool.

Important Considerations for Retaining Functionality:

• LED Bulbs Required: To retain both reverse lights and both rear fog lights, you must have LED bulbs installed in both locations. Halogen bulbs will not allow for this dual functionality.

Assembly Modification

Most North American Alltrack models already have the housing for a rear fog light bulb. If yours doesn’t, purchase European-spec tail light assemblies. If your assembly has the housing, you’ll need to remove a plastic obstruction that prevents the bulb from fitting. Use a Dremel to carefully remove this obstruction, ensuring the bulb fits properly afterwards.

Wiring and Adapter Installation

You can either route the wiring harness through the hatch panel using a snake tool or partially remove the panel for easier access. Four T20 Torx screws secure the panel. Once the wires are routed, connect the adapters. The wiring diagram provided above illustrates the factory configuration and necessary modifications. Remember, jumpers are only required for symmetrical reverse and fog light operation with LED bulbs. If symmetry is not a concern, simply swap the grey/black wire from pin 4 to pin 5 on the driver-side harness.

VCDS Coding Procedure

Using your VCDS cable and software, follow these steps:

Important Note: Coding procedures may vary slightly depending on your Alltrack’s build date. Refer to the build date information below to determine the correct method.

Build Dates and Corresponding Methods:

• 09/2016 & 11/2016: Coding modification via “Coding – 07”
• 04/2017: Coding modification via “Adaptation – 10”

General Coding Steps:

1. Security Access: Go to Module 09 – Central Electrics, then Security Access – 16. Enter access code 31347 and click “Do It!”.

2. Enabling Rear Fog Light Switch (If Necessary):

   • For “Coding – 07” Method: Go to Coding – 07, then Long Coding Helper. Enable Bit 4 in Byte 7 (“Light Switch with Rear Fog”) and click “Do It!”.
   • For “Adaptation – 10” Method: Search for “Außenlicht_uebergreifend-LDS_mit_Nebel_Schlusslicht”. Change the value to “Yes” and click “Do It!”.

3. Activating Rear Fog Light Function:

   • Search for “Leuchte28RFL LC11-Lichtfunktion A28”.
   • Change the value to “Nebelschlusslicht wenn kein Anhaenger gesteckt” (Rear fog light when no trailer is connected) and click “Do It!”.

4. LED Rear Fog Light Configuration (For LED Bulbs):

   • Search for “Leuchte28RFL LC11-Lasttyp 28”.
   • Change the value to “1 – LED Tagfahrlichtmodul Versorgung” (LED daytime running light module supply) and click “Do It!”.

5. Disabling Fog/Reverse Lights with Open Hatch (Optional):

   • Search for “Leuchte28RFL LC11-Lichtansteuerung HD AB 28” and change the value to “only_if_closed”. Click “Do It!”.
   • Search for “Leuchte29RFL RA64-Lichtansteuerung HD AB 29” and change the value to “only_if_closed”. Click “Do It!”.

Verification

After completing the coding, verify the functionality of your newly installed rear fog lights. They should illuminate when the switch is activated and the headlights are on. Congratulations, you’ve successfully added a valuable safety feature to your Volkswagen Alltrack!