This procedure covers the removal and replacement of the engine bay fuse box (Battery Junction Box) on a 2011-2014 Ford F-150 with the 3.5L EcoBoost engine.

Warnings

Tools required

Parts

• Engine bay fuse box (Battery Junction Box) × 1 — Use OEM specification - BL3Z-14290-B or equivalent
• Fuse box cover seal (if damaged) × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Turn ignition to OFF position and remove key
3. Open hood and secure with prop rod
4. Allow engine to cool completely if recently operated
5. Photograph the fuse box cover and all visible connections for reference
6. Note radio security code if applicable

Procedure

1. 1

   Disconnect battery
   Loosen the negative battery terminal bolt using a 10mm socket. Remove the negative cable from the battery post and secure it away from the terminal. Wait a minimum of 10 minutes for the electrical system to fully discharge before proceeding.
   Torque spec

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

   Remove fuse box cover
   Release the locking tabs on the fuse box cover and lift it off. The cover is located on the passenger side of the engine bay near the firewall. Set aside the cover and note the seal condition.
3. 3

   Document fuse and relay positions
   Before removing any fuses or relays, take clear photographs of their exact positions. The fuse box diagram is on the underside of the cover, but actual installed components may vary. Remove all fuses and relays, placing them in a labeled container or tray to maintain organization.
4. 4

   Disconnect main power cables
   Locate the large power distribution cables on top of the fuse box. Using a 13mm socket, remove the terminal bolts securing the main power feeds. There are typically 3-4 large cables. Support the cables as you remove them to prevent stress on the wiring. Label each cable position with tape for reassembly.
   ⚠These cables carry battery voltage even with negative terminal disconnected until removed. Handle carefully
   Torque spec

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

   Disconnect electrical connectors
   Locate all electrical connectors on the sides and bottom of the fuse box. There are typically 6-8 large multi-pin connectors. Press the locking tabs and carefully disconnect each connector. Some connectors have secondary locks that must be released first. Take photos of each connector before removal showing its exact orientation and position.
6. 6

   Remove ground connections
   Locate the ground strap connections attached to the fuse box mounting bracket. Using a 10mm socket, remove the ground strap bolts. Clean the ground contact surfaces with a wire brush to ensure good electrical contact during reassembly. Note the exact stacking order of any washers or multiple ground straps.
   ℹ️Clean ground connections are critical for proper electrical system operation
   Torque spec

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

   Remove mounting bolts
   Locate the fuse box mounting bolts securing it to the bracket. There are typically 2-3 bolts depending on configuration. Use a 10mm socket to remove the mounting bolts. Support the fuse box as you remove the final bolt to prevent it from falling.
   ⚠The fuse box is heavy with all cables still attached at this point. Support it carefully
   Torque spec

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

   Remove fuse box from vehicle
   Carefully lift the fuse box assembly out of the engine bay. You may need to maneuver it around other components. Work slowly to avoid damaging any remaining connected wiring. Place the old fuse box on a clean work surface for reference during installation.
9. 9

   Prepare new fuse box
   Inspect the new fuse box for any shipping damage. Verify part number matches the original. Do not transfer fuses or relays yet. Compare the new fuse box to the old one to confirm all connector positions match. Clean the mounting bracket and ground contact points on the vehicle.
10. 10

    Install new fuse box
    Position the new fuse box into the mounting bracket, ensuring it sits flush and aligned with all mounting holes. Start all mounting bolts by hand to ensure proper thread engagement, then tighten to specification using a torque wrench.
    Torque spec

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

    Reconnect ground connections
    Attach the ground straps to the fuse box mounting points in the exact order they were removed. Ensure the contact surfaces are clean and free of corrosion. Torque the ground strap bolts to specification. This is a critical connection for proper electrical system function.
    Torque spec

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

    Reconnect electrical connectors
    Using your reference photos, reconnect all multi-pin electrical connectors to the fuse box. Ensure each connector is fully seated and the locking tabs click into place. Verify any secondary locks are engaged. Gently tug on each connector to confirm it is secure.
13. 13

    Reconnect main power cables
    Using your labels and photos, reconnect the main power distribution cables to the correct terminals on top of the fuse box. Install the terminal bolts and torque to specification. Verify each cable is properly seated on its post before tightening.
    ⚠Incorrect power cable connections can cause serious electrical damage or fire. Verify positions carefully
    Torque spec

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

    Install fuses and relays
    Using your photos and the fuse box diagram, install all fuses and relays in their correct positions. Verify each fuse rating matches the original location. Replace any blown fuses with the correct amperage rating. Ensure all relays are fully seated.
15. 15

    Reconnect battery and test
    Reconnect the negative battery cable to the battery post. Torque the battery terminal bolt to specification - do not overtighten as this can damage the terminal. Turn the ignition to ON position (do not start engine) and verify all warning lights illuminate normally then extinguish. Check for any unusual smells or smoke indicating a short circuit.
    ⚠️If you smell burning or see smoke, immediately disconnect the battery and inspect all connections
    Torque spec

    Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Install the fuse box cover ensuring the seal is properly positioned
2. Start the engine and verify all electrical systems function normally
3. Test headlights, turn signals, brake lights, and all accessory functions
4. Reset clock and radio presets as needed
5. Clear any diagnostic trouble codes that may have been set during the procedure

Verification

• Start the engine and let it idle for 2 minutes, monitoring for any unusual electrical behavior
• Verify all dashboard warning lights extinguish normally after startup
• Test all major electrical systems: headlights, turn signals, wipers, power windows, HVAC blower
• With engine running, verify charging system shows 13.5-14.5 volts at battery
• Check for proper operation of electronic throttle control and turbochargers
• Scan for diagnostic trouble codes using an OBD-II scanner and address any codes present
• Verify no corrosion or heat damage is visible at any fuse box connections
• Confirm fuse box cover is properly sealed to prevent water intrusion

More procedures for this vehicle