2017-2019 Subaru Impreza Headlight Module: AFS/SRH Failure and Programming Guide
This guide covers common failures, diagnostic codes, and the critical programming requirements for the headlight control module in your 2017-2019 Subaru Impreza with LED headlights.
- This module is ONLY for 2017-2019 Impreza models with LED-based Adaptive Front-lighting System (AFS) / Steering Responsive Headlights (SRH).
- A replacement module (new or used) MUST be programmed and calibrated to the vehicle by a dealer or qualified shop with Subaru-specific scan tools.
- The most common failure symptom is a flashing 'AFS OFF' or 'SRH Disabled' warning light on the dashboard.
- The major headlight recall for this vehicle (NHTSA 22V-624) applies only to halogen headlights and is not related to this module or the LED system.
Compatibility Warning: LED Headlights Only
Important: This Headlight Control Module (part numbers 84051FL020, 84051FL021) is only for 2017-2019 Subaru Impreza models equipped with factory LED headlights, also known as Steering Responsive Headlights (SRH) or Adaptive Front-lighting System (AFS). It will not work on vehicles with standard halogen headlights. Always verify your vehicle's headlight type before purchasing.
Symptoms of a Failing Headlight Control Module
When the headlight control module begins to fail, it will typically trigger very specific warnings and behaviors. Here are the most common signs:
- "AFS OFF" or "SRH Disabled" Warning Light: 🎬 Watch this overview of causes and fixes for the SRH warning The most common symptom is a flashing or solid warning light on your instrument cluster. This indicates the adaptive system has a fault and has been disabled.
- Headlights Aimed Low: The headlights may default to their lowest possible position to avoid potentially glaring other drivers. This will significantly reduce nighttime visibility.
- Headlights Don't Swivel: The steering-responsive feature will stop working, and the headlights will no longer turn with the steering wheel.
- One or Both Headlights Inoperative: In some cases, a complete failure of the module can prevent one or both headlights from turning on at all.
- Diagnostic Trouble Codes (DTCs): A professional scan tool may reveal specific codes stored in the system. Common codes include U-series (communication) errors like U0073 or U0140, and B-series (body) codes like B2900 for an internal module error.
Known Issues, TSBs, and Recalls
Headlight Recall WRG-22 (NHTSA 22V-624) - Does NOT Apply
Subaru issued a major recall for 2017-2019 Impreza models due to faulty headlight reflectors that provided poor illumination. However, this recall, known as WRG-22, only applies to vehicles with halogen headlamps. Vehicles equipped with the LED headlights that use this control module are not affected by this specific recall.
Moisture Intrusion
Like many electronic modules, the Headlight Control Module is vulnerable to water damage. A Subaru Technical Service Bulletin (TSB) for other models, 07-111-16, noted a design change to improve headlamp assembly sealing against moisture. If a headlight housing develops a leak, water can get into the assembly and damage the control module or its connectors, leading to failure.
Programming and Calibration: A Dealer Visit is Required
Warning: A replacement Headlight Control Module, whether new or used, is NOT plug-and-play. The module must be programmed and initialized to the vehicle after installation.
This process, often called "initialization" or "calibration," electronically registers the new module with the car's Body Integrated Unit (BIU) and other systems. It establishes a baseline for the vehicle's ride height sensors, which is critical for the auto-leveling function to work correctly.
This procedure requires a Subaru-specific diagnostic tool, like the Subaru Select Monitor (SSM), or a high-end professional scan tool with the correct software. For this reason, a trip to a Subaru dealership or a qualified independent shop specializing in Subaru repairs is necessary to complete the installation. Failure to program the module will result in the AFS/SRH system remaining disabled and the warning light staying on.
Buying a Used Headlight Control Module
A used OEM module is an excellent, cost-effective alternative to a brand-new part. Since these modules are generally reliable until they suffer from damage (like water intrusion), a used unit from a reputable source is a smart choice. Here's what to look for:
- Verify the Part Number: Double-check that the part number on the used module matches your original one. The known part numbers are 84051FL020 and 84051FL021.
- Inspect for Corrosion: Carefully examine the electrical connector pins for any signs of green or white corrosion, which indicates past moisture exposure. Do not buy a module with corroded pins.
- Check the Casing: Look for any cracks, warping, or signs that the case has been opened. A physically damaged module should be avoided.
- Budget for Programming: Remember to factor in the cost of having the module professionally programmed. Call local dealerships or specialty shops for a quote before you buy the part.
Replacement Cost Breakdown
The cost to replace a Headlight Control Module can vary significantly based on your choice of part and local labor rates. The most significant cost factor is often the programming required after installation.
| Item | Estimated Cost |
|---|---|
| New OEM Module (Part Only) | $450 - $600 |
| New Aftermarket Module | Not Commonly Available |
| Used OEM Module | $50 - $150 |
| Shop Labor & Programming | $170 - $350 |
| Total (with Used OEM) | $220 - $500 |
| Total (with New OEM) | $620 - $950 |
Estimates are based on available market data and may vary by location and supplier.
Frequently Asked Questions (FAQ)
Where is the Headlight Control Module located on a 2017-2019 Impreza?
The AFS/SRH control module is typically a small blue or white plastic box located in the driver's side footwell. You will need to remove the lower dash trim panel and kick panel near the emergency brake pedal to access it.
Can I install a used module myself and then drive to the dealer?
Yes. The physical installation is straightforward for a DIY mechanic. After you swap the module, the headlights will likely function in a basic, low-beam mode, allowing you to safely drive the vehicle to a dealership or shop for the final programming and calibration.
Is the Headlight Control Module the same as a ballast?
No. A ballast (or igniter) is a component specific to High-Intensity Discharge (HID) headlights that provides the high voltage needed to start the bulb. The Headlight Control Module is a computer that controls the aiming and leveling motors for the adaptive LED headlight system. The two parts serve entirely different functions.
Can I just unplug the module to get rid of the 'AFS OFF' light?
Unplugging the module will disable the system and may turn off the blinking light, but it is not a proper fix. This will leave your headlights in a fixed, uncalibrated position, likely aimed too low, and you will lose all adaptive safety features. 🎬 Watch how to disable the AFS warning light with aftermarket lights The correct solution is to diagnose and repair the system.
Helpful Videos
Technical Specifications
OEM Part Numbers: 84051FL020 84051FL021
Controls the Adaptive Front-lighting System (AFS) / Steering Responsive Headlights (SRH). Requires CAN bus integration and initialization to vehicle level sensors.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Subaru Impreza:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Compatibility Warning: LED Headlights Only
- Symptoms of a Failing Headlight Control Module
- Known Issues, TSBs, and Recalls
- Headlight Recall WRG-22 (NHTSA 22V-624) - Does NOT Apply
- Moisture Intrusion
- Programming and Calibration: A Dealer Visit is Required
- Buying a Used Headlight Control Module
- Replacement Cost Breakdown
- Frequently Asked Questions (FAQ)
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