Tesla Model S & X Headlight Module Failure (2021-2025): A Guide to Replacement and Programming

Headlight Technology in the Refreshed (2021+) Model S and X

The 2021 model year marked a significant refresh for the Tesla Model S and Model X, sometimes referred to as the "Palladium" update. A key part of this update was the introduction of a more advanced, fully LED-based headlight system. These are not simple LED bulbs but complete, sealed assemblies with adaptive capabilities. Depending on the vehicle's configuration and date of manufacture, this can include Matrix or Global headlight technology 🎬 See a full DIY Matrix headlight retrofit walkthrough that adjusts the light pattern to avoid dazzling other drivers while maximizing illumination. The Headlight Control Module is the brain that makes these features possible, interpreting data from the vehicle's cameras and sensors to control the light output.

Common Symptoms of a Failing Headlight Control Module

A faulty headlight control module can cause a range of issues, from a minor annoyance to a critical safety problem. Because the module controls multiple functions, you may experience one or more of the following symptoms, typically on just one side of the vehicle:

• Complete or Partial Headlight Failure: The low beam, high beam, or amber turn signal may stop working entirely.
• Flickering Lights: The headlight may flicker intermittently, sometimes triggered by specific temperatures.
• Dashboard Warning Messages: The car will often report the fault with a generic "Headlight malfunction detected" message or a more specific alert like "Right headlight malfunction detected". Specific service alert codes, such as BC_w005, may also be logged.
• Loss of Adaptive Functions: The headlights may stop swiveling when you turn the steering wheel, or the auto high-beam feature may become disabled. Note that this can also be caused by a dirty windshield blocking the forward-facing camera.
• Burnt Smell or Corrosion: In cases of water intrusion, you may notice a distinct electrical burning smell or visible green corrosion on the module's connector pins if you remove it for inspection.

Known Issues, Recalls, and Technical Service Bulletins (TSBs)

NHTSA Recall 24V-904 (Tesla Service Bulletin SB-24-00-017)

This recall specifically affects a small batch of 25 Tesla Model X vehicles manufactured between June 5, 2024, and August 2, 2024. The issue involved the low beam headlights and parking lights flickering in certain low-temperature conditions. According to the NHTSA report, the problem was caused by a unique combination of a software issue and headlamp hardware that was produced near the edge of its design specifications. Tesla addressed this issue by deploying an over-the-air (OTA) software update to all affected vehicles, which resolved the problem without requiring a physical repair. The recall identifies the specific headlamp assembly part numbers as 1800040-00-C (Left Hand) and 1800041-00-C (Right Hand).

Buying a Used Headlight Control Module: What to Look For

Given the high cost of a new headlight assembly from Tesla, a used OEM module is an excellent cost-saving alternative. Unlike many complex electronics, a used module can be made to work perfectly if you follow the correct procedure. Here’s what to check:

• Match the Part Number: This is the most critical step. The module is typically mounted to the bottom of the headlight assembly. You may need to remove the old module to find the part number printed on its label. Match this number exactly to ensure you are buying a compatible part.
• Inspect the Connector Pins: Ask the seller for a clear photo of the electrical connector port. Look for any signs of white or green corrosion, or bent/damaged pins. A clean connector is essential for reliable operation.
• Check the Housing: Look for cracks or damage to the plastic or metal casing. A compromised housing can allow moisture to enter and destroy the internal circuit board.
• Understand Left vs. Right: While the modules for the left and right headlights may look identical and even share the same physical footprint, they are programmed for a specific side. You must install a right-side module on the right headlight and a left-side module on the left. Installing a module on the wrong side will cause it to not function until a full software reinstall is performed.

Replacement and Programming

Replacing the headlight control module is an advanced DIY task, primarily because of the mandatory software steps required after installation.

1. Physical Installation

There are two main approaches to accessing the module, which is attached to the bottom of the headlight housing with several Torx screws.

• Fender Liner Method: Some DIY mechanics have successfully accessed the module by turning the front wheel, removing the plastic fender liner clips, and reaching up behind the headlight assembly. This avoids removing the bumper but offers very limited working space.
• Bumper Removal Method: The official Tesla service procedure requires removing the front fascia (bumper) and then removing the entire headlight assembly from the vehicle. This provides clear access to the module but is a much more involved job.

2. Mandatory Software Reinstallation

This is the step that trips up most people. You must put the car into "Service Mode" and trigger a software reinstall. This forces the car's computer to scan for and configure new hardware, including the replacement headlight module.

1. On the main touchscreen, navigate to Controls > Software.
2. Press and hold the model name (e.g., "Model S") for a few seconds until a password prompt appears.
3. Enter the access code "service".
4. In the Service Mode menu, find the option for Software Reinstall and initiate the process.
🎬 Watch this guide to software reinstall after replacing a headlight
5. The process can take anywhere from five minutes to over an hour, during which the car will be inoperable. Once complete, the new headlight module should be recognized and functional.

3. Headlight Aiming and Calibration

After replacing the module or the entire headlight assembly, you must adjust the headlight aim. This is also done through the Service Mode menu.

On the touchscreen, go to Controls > Service > Adjust Headlights. This will bring up an interface that allows you to use the steering wheel scroll wheels to adjust the beam height and direction. While you can perform a basic alignment against a wall, for perfect results that comply with regulations, the adjustment should be done using a professional headlight aiming tool.

Frequently Asked Questions (FAQ)