2016-2020 Tesla Model S & Model X 12V Fuse Box: Solving Electrical Gremlins

Understanding the Fuse Box System in Your Tesla

Unlike traditional cars with a single main fuse box, the 2016-2020 Tesla Model S and Model X utilize a distributed system with two primary low-voltage fuse boxes. It is crucial to identify which box is causing issues. Both are shared between the Model S and Model X platforms from this era, but their locations can differ.

• Underhood Fuse Box (Frunk): Located in the front trunk under a cover, this box handles high-current 12V circuits like power steering, ABS, and feeds to the cabin. It is identifiable by part numbers starting with 1034405 or 1094405.
• Cabin Fuse Box: This unit is more than just a fuse holder; it's an intelligent junction box or body control module that manages many of the vehicle's interior electronic features. It is typically identified by part numbers starting with 1094409.

This guide will focus primarily on the Cabin Fuse Box, as its failure often causes a wider range of intermittent electronic issues and has specific replacement requirements. We will also cover key details about the Underhood Fuse Box.

Symptoms of a Failing 12V Fuse Box

A failing fuse box often creates bizarre and seemingly unrelated electrical problems. Because it controls so many different circuits, a single internal fault can have widespread effects.

• Multiple Accessory Failures: One of the most common signs is when several components stop working at once. This could include power windows, interior lights, the radio, seat heaters, or the 12V power outlets.
• Intermittent Component Function: You might find that certain features work one moment and not the next. This can be caused by corrosion or a cracked solder joint inside the fuse box creating a poor connection.
• Warning Lights on the Dash: A failing fuse box can trigger warnings for the Tire Pressure Monitoring System (TPMS), ABS, or Traction Control if the modules for those systems lose power or communication.
• Blown Fuses: While a single blown fuse is normal, if a new fuse for the same circuit blows immediately or repeatedly, it may indicate a short within the fuse box itself rather than the component.
• Visible Corrosion or Water Damage: Water intrusion is a known enemy of vehicle electronics. On early Model S vehicles, the A/C drain hose could sometimes drip onto high-voltage components, leading to rust on fuse box covers and moisture getting inside. Any sign of white or green crust on the connectors or pins is a major red flag.

Compatibility and Part Numbers (2016-2020)

Compatibility is critical when sourcing a replacement fuse box. Always verify the part number from your original unit before ordering a used part. These parts are for the 'pre-refresh' Model S and Model X and will not fit the redesigned 2021 and newer models.

Cabin Fuse Box (Part # 1094409-xx-x)

This module is located inside the passenger compartment. Its location varies by model:

• 2016-2020 Tesla Model S: Located on the front passenger's side, behind the kick panel or sill panel by the floor.
🎬 Watch this step-by-step walkthrough for replacing the cabin module.
• 2016-2020 Tesla Model X: Located on the driver's side, to the right of the accelerator pedal, 🎬 Watch this quick guide to accessing and replacing interior fuses. behind the center console side trim.

Known part numbers include 1094409-00-E, 1094409-00-G, 1094409-01-E, and 1094409-01-G. The final letter indicates a revision, with later letters in the alphabet representing newer versions. It is generally safe to install a newer revision (e.g., replacing an '-E' with a '-G').

Underhood Fuse Box (Part # 1094405-xx-x)

This fuse box is located in the frunk (front trunk) of both the Model S and Model X, under the main plastic cover near the windshield. Known part numbers include 1094405-02-D and 1094405-02-E.

Buying a Used Fuse Box: What to Look For

A used OEM fuse box can be a reliable and cost-effective solution, especially since quality aftermarket options are nonexistent. Here’s what to check:

1. Match the Part Number Series: Do not interchange an Underhood box (1094405) with a Cabin box (1094409). They serve different functions and are not compatible. Match your original part number as closely as possible.
2. Inspect for Corrosion: This is the most important check. Carefully examine all electrical pins and connectors. Look for any white, green, or blueish powder or discoloration. Do not buy a fuse box with any signs of water damage.
3. Check for Melted Plastic: Look closely at the sockets where fuses and relays plug in. Any melted or deformed plastic indicates a past overheating event, and the box should be rejected.
4. Verify the Source Vehicle: If possible, avoid parts from flood-damaged vehicles. A reputable recycler will provide the VIN of the donor car, which you can use to check its history.

Programming and Installation Requirements

This is the most critical question for any electronic module replacement.

The Cabin Fuse Box (1094409-xx-x) requires programming. After physical installation, the vehicle's configuration must be updated to recognize the new module. This procedure typically requires Tesla's proprietary "Toolbox" diagnostic software. While a DIYer can physically swap the part, the final programming step will likely require a visit to a Tesla Service Center or a qualified independent repair shop that specializes in Teslas and has access to the necessary software.

The Underhood Fuse Box (1094405-xx-x) is generally considered a more straightforward replacement and may not require software programming, but you must pay close attention to the potential need for the rework procedure mentioned above.

Cost Comparison

Pricing for these components can vary, but here is a general expectation:

Recalls and Service Bulletins

As of early 2026, there are no specific NHTSA recalls for the 12V fuse boxes on the 2016-2020 Tesla Model S or Model X. Most recalls for these vehicles have been related to software-correctable issues (like FSD behavior or warning light fonts) or other mechanical components like power steering.

Frequently Asked Questions (FAQ)