This procedure covers the replacement of the main relay (also known as the power distribution box relay) in the engine compartment of a 2015-2020 Ford F-150 with the 3.5L EcoBoost V6 engine.

Warnings

Tools required

Parts

• Main relay (PCM power relay) × 1 — Ford DY-1214 or equivalent

Preparation

1. Park vehicle on level ground and engage parking brake
2. Turn ignition to OFF position and remove key
3. Allow engine to cool completely if recently operated
4. Open hood and secure with prop rod
5. Locate the power distribution box on the driver's side of the engine compartment near the firewall

Procedure

1. 1

   Disconnect battery negative terminal
   Using a battery terminal wrench or 8mm socket, loosen the negative battery terminal bolt. Remove the negative cable from the battery post and position it away from the terminal to prevent accidental contact. Wait at least 2 minutes for the electrical system to discharge.
   Torque spec

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

   Access the power distribution box
   Locate the power distribution box on the driver's side of the engine bay. The box is a black plastic housing with multiple relays and fuses. Identify the cover release tabs on both sides of the box.
3. 3

   Remove power distribution box cover
   Press the release tabs on both sides of the power distribution box cover simultaneously and lift the cover straight up to remove it. The cover has a diagram on the underside showing relay and fuse locations. Set the cover aside in a clean location.
4. 4

   Identify the main relay location
   Reference the diagram on the underside of the cover or in the owner's manual to locate the main PCM power relay. This is typically a larger relay in the box, often labeled as 'PCM PWR RLY' or relay position R2. Note the orientation of the relay before removal.
5. 5

   Remove the old main relay
   Grasp the relay firmly between thumb and forefinger, or use a relay puller tool if available. Rock the relay gently side to side while pulling straight up with steady, even pressure. Do not twist or bend the relay. Remove the relay completely from its socket.
6. 6

   Inspect the relay socket
   Examine the relay socket terminals for any signs of corrosion, burning, melting, or damage. Check that all terminal pins are straight and properly seated. If corrosion is present, clean gently with electrical contact cleaner and allow to dry. If terminals are damaged, the entire power distribution box may need replacement.
7. 7

   Install the new main relay
   Align the new relay with the socket, ensuring the orientation matches the original relay and the diagram on the cover. The relay will only fit one way due to the terminal configuration. Apply light pressure and push the relay straight down into the socket until it seats completely with an audible click. Ensure the relay is fully seated and flush with surrounding relays.
8. 8

   Reinstall power distribution box cover
   Position the cover over the power distribution box, aligning the tabs with the slots on the box. Press down firmly on both sides until the tabs click into place. Verify the cover is secure by attempting to lift it gently.
9. 9

   Reconnect battery negative terminal
   Clean the battery terminal post and cable end if necessary. Place the negative cable onto the negative battery post and hand-tighten the terminal bolt. Using a torque wrench, tighten the battery terminal bolt to specification. Ensure the connection is secure but do not overtighten.
   ⚠Do not overtighten battery terminal bolts as this can crack the battery case or damage the terminal
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Ensure all electrical connections are secure and properly seated
2. Verify the power distribution box cover is fully latched
3. Confirm no tools or parts have been left in the engine compartment

Verification

• Turn the ignition key to the ON position (do not start) and verify the instrument cluster illuminates normally
• Check for any warning lights or fault codes related to the PCM or electrical system
• Start the engine and verify it starts normally without hesitation or fault codes
• Allow the engine to idle for 2-3 minutes and verify all electrical systems (lights, radio, accessories) function properly
• Turn off the engine and restart to confirm consistent operation
• If any fault codes appear, use a diagnostic scanner to verify they are not related to the relay replacement

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