Volkswagen’s Mk6.5 Jetta, a popular sedan known for its blend of economy and features, often becomes a canvas for owners looking to personalize and upgrade their vehicles. One common modification involves enhancing the lighting system, particularly for those wanting to adopt the European style taillights with amber turn signals and rear fog lights. This guide delves into a specific challenge faced by a Mk6.5 Jetta owner during a taillight retrofit, focusing on maintaining the functionality of front LED Daytime Running Lights (DRL) and parking lights.
The Taillight Upgrade and Unexpected Front Lighting Problems
The owner of a 2017 VW Jetta GLI SE (Mk6.5), equipped with factory full LED taillights (NAR – North American Region), LED license plate lights, and halogen front headlights with integrated LED DRL and parking lights, decided to retrofit European-spec taillights. The goal was to gain the sought-after amber turn signals and rear fog light functionality, features often preferred over the NAR specifications.
After successfully wiring the new European taillights, the user utilized VCDS (VAG-COM Diagnostic System) to adjust the Body Control Module (BCM) settings. Specifically, they changed Byte 18, a common step in taillight retrofits, to “8C – Jetta ROW (Rest of World).” This selection seemed logical as it aligned with Jettas outside North America that share a similar lighting configuration.
While the rear taillights functioned perfectly after this coding change – with turn signals, brake lights, reverse lights, and parking lights all working without error codes – an unexpected issue arose at the front of the car. The LED DRLs and parking lights ceased to function, triggering four error codes. Notably, the front fog lights, low beams, and high beams remained unaffected. The user also observed that in the parking light position on their European headlight switch, only the side marker lights (a US regulation requirement) illuminated at the front.
Decoding Byte 18 and Seeking the Correct Configuration
Extensive research led the owner to understand that the “8C” coding in Byte 18, while suitable for ROW Jettas, is intended for models with separate incandescent parking lights and DRLs. This configuration differs from their NAR-spec Mk6.5 Jetta GLI SE, which utilizes a combined LED DRL and parking light setup within the headlight housing.
The user then identified “Hex 90” as a potentially more appropriate coding option. Here’s a breakdown of the two hexadecimal options and their descriptions within VCDS:
- Hex 90: VW465 FL Halogen/XENON VW368 RdW TFL_1_LED ROM 144 (VW465 FL Halogen / Xenon VW368 RdW TFL_1_LED ROM 144)
- Hex 8C: VW361 Halogen/XENON VW361 RdW TFL_1 ROM 140 (VW361 Halogen / Xenon VW361 RdW TFL_1 ROM 140)
The key difference highlighted is “TFL_1” versus “TFL_1_LED.” “TFL” is German abbreviation for Tagfahrlicht, which translates to Daytime Running Light. The user correctly deduced that “TFL_1_LED” is likely the necessary setting to inform the BCM that the vehicle is equipped with LED DRLs.
The Core Question: LED DRL and Parking Light Coding for Mk6.5 Jetta
The central question becomes: How to properly configure Byte 18 in the BCM of a Mk6.5 Jetta GLI SE with factory LED DRL and parking lights to accommodate European taillight retrofit without losing front lighting functionality?
The user needs to determine if “Hex 90” or another hexadecimal code within Byte 18 will correctly signal to the BCM that the vehicle has combined LED DRL and parking lights. This correct coding is crucial to restore the front lighting and eliminate the error codes triggered after the initial Byte 18 modification for the European taillight retrofit. Further investigation and potentially expert advice are needed to confidently adjust Byte 18 and resolve this Mk6.5 Jetta lighting puzzle.
