Audi & VW Headlight Control Module Guide: A4, Q5, Jetta, Golf & More (1999-2020)

Understanding "Headlight Control Module" on Your VW or Audi

Before diagnosing a headlight problem, it's critical to know which module you're dealing with. The vehicles in this guide use several different types of modules, and they are not interchangeable.

• HID Ballast / LED Power Module: Found on vehicles with HID Xenon or LED headlights. This module is typically mounted directly on the back or bottom of the headlight assembly. Its job is to convert the car's 12V power into the high voltage needed to ignite a xenon bulb or to precisely regulate power for LED elements. A common part number for many 2008+ Audis and VWs is 8K0941597E.
• Headlight Range / AFS Control Module: Found on vehicles with auto-leveling or adaptive front lighting systems (AFS), which swivel the headlights into turns. This module takes input from level sensors on the suspension to aim the headlights correctly, preventing glare for oncoming drivers. On many Audis and VWs, this is part number 5M0907357G or a similar variant.
• Body Control Module (BCM) / Central Electronics Module (J519): This is the main computer for the vehicle's body electronics, including the headlights, taillights, turn signals, and interior lights. On many VW Jetta and Golf models, a failing BCM is the root cause of lighting issues. On Audis, this is often called the Central Electronics Control Module or J519. It is typically located under the dashboard on the driver's side.

Symptoms of a Failing Headlight Module

Symptoms can vary depending on which module is failing. Always check the simple things first: test the bulbs and check all related fuses before assuming a module is bad.

Symptoms of a Bad HID Ballast or LED Module

• One headlight flickers, changes color (often to a pinkish hue), or is dimmer than the other.
• Headlight works intermittently, sometimes not turning on until you cycle the switch multiple times.
• The headlight won't turn on at all, even with a known-good bulb.
🎬 See how to safely replace a faulty HID headlight ballast
• A buzzing or humming noise comes from the headlight assembly.
• Water damage or corrosion is visible on the module, which is common as they are exposed to the elements on the headlight housing.

Symptoms of a Bad Range / AFS Module

• A "Headlight Range Defective" or similar warning message on the dashboard.
• Headlights aim straight down and do not perform their self-test sweep up and down when the car is started.
• Adaptive headlights no longer turn with the steering wheel.
• Associated OBD-II codes related to headlight leveling sensors or the module itself.

Symptoms of a Bad Body Control Module (BCM)

• Multiple, unrelated lighting failures (e.g., a headlight and a taillight go out simultaneously).
• Turn signals blink rapidly as if a bulb is out, but all bulbs are fine.
• Low or high beams do not work, or do not switch properly. A 2015 VW Jetta recall was issued for a software glitch where low beams would turn off when high beams were activated.
• Other electrical issues like power windows, door locks, or wipers malfunctioning, since the BCM controls these as well.

Platform-Specific Information, Recalls, and TSBs

The specific module and its issues can vary greatly by vehicle generation.

Audi B8/B8.5 Platform (2008-2017 A4, S4, A5, S5, Q5)

These models most commonly suffer from failures of the HID ballast (part no. 8K0941597E or similar 🎬 Watch this step-by-step Audi headlight ballast replacement tutorial) or the Headlight Range Control Module (part no. 8K0907357B or similar). The ballast is mounted to the bottom of the headlight housing and is prone to water damage. The range control module is typically located inside the car, behind the glovebox, making it less susceptible to moisture but more difficult to access. A Technical Service Bulletin (TSB) was issued for 2013+ A4 models regarding customer perception of the xenon headlight beam being too low, which is considered a normal characteristic of a design change.

Volkswagen PQ35/PQ46 Platforms (2005-2018 Jetta, Golf, etc.)

On these models, lighting problems are very often traced to the Body Control Module (BCM), located under the driver's side dashboard, behind the fuse panel. These modules come in many different part numbers (e.g., 1K0937087) with different software versions depending on the car's options. It is critical to match the part number exactly or use a compatible, newer revision. A recall was issued for some 2015 Jettas to update the headlight control module software. Another recall affected a small number of 2019 Jettas for incorrectly positioned passenger headlights.

Audi C7 & Q7 Platforms (2010-2018 A6, A7, Q7)

These vehicles use more advanced lighting systems. Failures can involve the main J519 Central Electronics module, individual headlight power modules, or AFS range modules. A recall was issued for some 2017 A4 and Q7, 2015-2017 Q3, and other models for a software issue that could cause the side marker lights to be inoperative. Many modules on these platforms are subject to Component Protection (see below).

Programming, Coding, and Component Protection

This is the most critical part of replacing an electronic module on a modern VW or Audi.

• Coding: Most BCMs and Headlight Range modules need to be 'coded' to the vehicle. This process uses a diagnostic tool (like VCDS or ODIS) to tell the module which features the car has (e.g., xenon vs. halogen, fog lights, etc.). A new module will often not work correctly until it is coded.
• Component Protection (CP): On newer Audis (roughly 2008+ on many models), critical electronic modules like the Gateway, MMI/Infotainment, and sometimes lighting modules are linked to the car's VIN as an anti-theft measure. If you install a used module with Component Protection, it will enter a restricted mode with limited or no function. Removing Component Protection must be done online by connecting to VW/Audi factory servers. While this was traditionally a dealer-only service, some specialized independent shops now have the tools to perform this adaptation.

Buying a Used Headlight Control Module

Buying a used OEM module can save you hundreds of dollars, but it requires careful attention to detail.

• Why Used OEM is Often Better: For complex electronics like BCMs and lighting modules, a used original equipment (OEM) part is often more reliable than a cheap aftermarket clone. The software and hardware are designed specifically for your vehicle, ensuring proper function after coding.
• Match the Part Number EXACTLY: This is the most important rule. VW and Audi use many different hardware and software versions of the same module. Using the wrong one can result in features not working or the module being incompatible. The part number is printed directly on the module's label (e.g., `1K0 937 087 AG` or `8K0 941 597 E`).
• Inspect for Corrosion: For modules mounted on the headlight itself (like HID ballasts), carefully inspect the casing and electrical connector pins for any signs of white or green corrosion. This is a clear sign of water intrusion and a high risk of failure.
• The Component Protection Gamble: If you are buying a module for a vehicle with Component Protection, understand that you will have an additional cost to have it adapted to your car. Factor this into the total price. A cheap used module that a dealer charges $200 to adapt may not be a good value.

Cost Comparison

Prices can vary dramatically based on the specific module your vehicle needs.

Frequently Asked Questions (FAQ)