This procedure covers the removal and replacement of the engine bay fuse box (Battery Junction Box) on a 2015-2020 Ford F-150 with the 3.5L EcoBoost engine, including disconnection of all electrical connectors and harnesses.

Warnings

Tools required

Parts

• Engine Bay Fuse Box Assembly (Battery Junction Box) × 1 — Use OEM specification
• Fuse box mounting hardware kit (if damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and engage parking brake
2. Turn off ignition and remove key fob from vehicle interior
3. Allow engine to cool completely if recently operated
4. Photograph the fuse box and all visible connectors from multiple angles for reference
5. Document or photograph the fuse and relay layout inside the fuse box cover
6. Have replacement fuse box available and verify part number matches application

Procedure

1. 1

   Disconnect battery negative terminal
   Open the hood and locate the battery. Using a 10mm socket, loosen and remove the negative battery terminal bolt. Remove the negative cable from the battery post and secure it away from the terminal to prevent accidental contact. Wait at least 2 minutes for capacitive discharge before proceeding.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
2. 2

   Disconnect battery positive terminal
   Using a 10mm socket, loosen and remove the positive battery terminal bolt. Remove the positive cable from the battery post. Note that this cable connects directly to the fuse box. Secure the cable away from the battery.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
3. 3

   Remove fuse box cover
   Release the locking tabs on the fuse box cover by pressing them inward while lifting the cover. Remove the cover completely and set aside. Remove all fuses and relays from the fuse box, placing them in a labeled container or on the cover in their original positions for reference.
   ℹ️Some fuses may be difficult to remove. Use a fuse puller tool or needle-nose pliers to avoid damage.
4. 4

   Disconnect main power feed cable
   Locate the large power distribution cable connected to the bottom of the fuse box (from the positive battery terminal). Remove the terminal bolt using the appropriate socket. Carefully pull the cable terminal away from the fuse box and secure it to prevent it from falling into the engine bay.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
5. 5

   Disconnect electrical connectors
   Working systematically, disconnect all electrical connectors from the fuse box. There are typically 6-8 large multi-pin connectors on the side and bottom of the fuse box. Press the locking tabs while pulling each connector straight out. For connectors with secondary locks, slide the red safety clip out before releasing the main lock.
   ⚠Do not force connectors. Ensure locking tabs are fully released before pulling. Some connectors may require sliding locks or rotating collars.
6. 6

   Disconnect ground strap
   Locate the ground strap attached to the fuse box mounting bracket or nearby body location. Using the appropriate socket, remove the ground strap bolt. Clean the ground contact surfaces with a wire brush to ensure proper connection during reassembly.
   Torque spec

   Ground Strap Bolts12 Nm (9 lb-ft)
7. 7

   Remove fuse box mounting bolts
   Locate the fuse box mounting bolts securing the assembly to the fender or inner fender structure. There are typically 2-3 mounting bolts. Using a 10mm socket, remove all mounting bolts and set aside. Support the fuse box with one hand as you remove the final bolt.
   Torque spec

   Module Mounting Bolts8 Nm (6 lb-ft)
8. 8

   Remove fuse box assembly
   Carefully lift the fuse box assembly up and out of the engine bay. The unit may be heavy and have remaining wiring that needs to be maneuvered through the mounting area. Inspect the mounting bracket and surrounding area for damage, corrosion, or debris. Clean the mounting surfaces as needed.
   ⚠The fuse box assembly weighs approximately 8-12 lbs. Support it carefully to avoid dropping it onto other engine components.
9. 9

   Prepare new fuse box
   If installing a new or remanufactured fuse box, verify the part number matches the original. Transfer any fuses or relays that are not included with the replacement unit, ensuring they are installed in the correct positions according to the diagram on the cover or your photos. Inspect all connector ports on the new fuse box for damage or debris.
   ℹ️Some replacement fuse boxes come pre-programmed, while others may require dealer programming. Verify requirements before installation.
10. 10

    Install fuse box assembly
    Position the new fuse box into the mounting location, carefully routing any attached wiring. Align the mounting holes with the bracket. Hand-start all mounting bolts before tightening any of them. Once all bolts are started, torque them to specification in a cross pattern.
    Torque spec

    Module Mounting Bolts8 Nm (6 lb-ft)
11. 11

    Reconnect ground strap
    Position the ground strap to the mounting point, ensuring the contact surface is clean and bare metal. Install the ground strap bolt and torque to specification. Ensure the connection is tight and free of paint or corrosion.
    Torque spec

    Ground Strap Bolts12 Nm (9 lb-ft)
12. 12

    Reconnect electrical connectors
    Reconnect all electrical connectors to the fuse box in reverse order of removal. Push each connector firmly until you hear or feel a click, indicating the locking tab has engaged. Engage any secondary locks or safety clips. Verify each connector is fully seated by attempting to gently pull it back out.
    ⚠Ensure connectors are oriented correctly. Do not force misaligned connectors as this will damage pins.
13. 13

    Reconnect main power feed cable
    Connect the large power distribution cable to the fuse box terminal. Ensure the contact surfaces are clean. Install the terminal bolt and torque to specification. Verify the connection is secure.
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)
14. 14

    Reinstall fuses and relays
    Install all fuses and relays in their correct positions according to the fuse box diagram and your reference photos. Ensure each fuse and relay is fully seated in its socket. Double-check that all high-amperage fuses are in the correct locations.
    ⚠Installing incorrect amperage fuses can result in electrical system damage or fire. Verify each fuse rating matches the diagram.
15. 15

    Reconnect battery terminals
    Connect the positive battery cable first, ensuring clean contact with the battery post. Install the terminal bolt and torque to specification. Then connect the negative battery cable and torque its bolt to specification. Do not overtighten battery terminals as this can damage the battery posts.
    ℹ️Always connect positive terminal first, then negative. This prevents accidental shorts.
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Install the fuse box cover by aligning the tabs and pressing firmly until all locking tabs click into place
2. Apply dielectric grease to battery terminals to prevent corrosion
3. Reset clock, radio presets, and any other vehicle settings as needed
4. If vehicle has keyless entry, ensure key fobs are recognized by the system

Verification

• Turn ignition to ON position (do not start) and verify all warning lights illuminate then extinguish normally
• Check operation of all electrical accessories: windows, locks, lights, wipers, HVAC blower, and radio
• Start the engine and verify it runs normally without warning lights
• Use a scan tool to check for any diagnostic trouble codes and clear if related to battery disconnect
• Test all lighting circuits including headlights, turn signals, brake lights, and hazard lights
• Verify power distribution by checking voltage at multiple fuse locations (should read battery voltage)
• Test charging system by checking battery voltage with engine running (should read 13.5-14.5 volts)
• Road test vehicle to verify all electrical systems function properly under driving conditions
• If new fuse box requires programming, verify all modules communicate properly using a scan tool

More procedures for this vehicle