This procedure covers the removal and replacement of the main relay (EFI relay) in the engine compartment fuse box for a 2018-2024 Toyota Camry with a 2.5L I4 engine.

Warnings

Tools required

Parts

• Main relay (EFI relay) × 1 — Use OEM specification - Toyota part number varies by specific model year

Preparation

1. Ensure the vehicle is parked on level ground with the parking brake engaged
2. Turn off all electrical accessories and remove the key from the ignition
3. Allow the engine to cool completely if recently driven
4. Open the hood and secure it with the hood prop

Procedure

1. 1

   Disconnect the battery negative terminal
   Using a 10mm socket, loosen 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 the electrical system to discharge.
   Torque spec

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

   Locate the engine compartment fuse box
   The main fuse box is located on the driver's side of the engine compartment, near the strut tower. It is a black rectangular box with a removable cover.
3. 3

   Remove the fuse box cover
   Release the clips securing the fuse box cover by pressing the tabs on both sides. Lift the cover straight up and set it aside in a clean area. Note the relay diagram on the underside of the cover for reference.
4. 4

   Identify the main relay location
   Locate the main relay (also labeled as EFI MAIN or similar) in the fuse box. It is typically a larger relay compared to standard fuses, positioned in the relay section of the box. Refer to the fuse box diagram on the cover or in the owner's manual for exact location.
5. 5

   Remove the main relay
   Firmly grasp the main relay by its plastic body. Pull straight upward with steady, even pressure to extract the relay from its socket. Do not rock the relay side to side as this may damage the socket terminals. Inspect the old relay for signs of burning, corrosion, or physical damage.
6. 6

   Inspect the relay socket
   Examine the relay socket terminals for corrosion, discoloration, or damage. If corrosion is present, use electrical contact cleaner and a small brush to clean the terminals. Ensure all socket pins are straight and properly positioned.
   ⚠If socket terminals are damaged or severely corroded, the entire fuse box may require replacement. Do not attempt to bend damaged terminals.
7. 7

   Install the new main relay
   Align the new relay with the socket, ensuring the relay pins match the socket orientation. The relay will only fit one way. Press the relay firmly into the socket until it is fully seated and flush with the surrounding relays. You should feel a positive click when properly installed.
8. 8

   Reinstall the fuse box cover
   Position the fuse box cover over the fuse box, aligning the clips with their receivers. Press down firmly on both sides until all clips engage with an audible click. Verify the cover is secure and sits flush.
9. 9

   Reconnect the battery negative terminal
   Place the negative battery cable back onto the negative battery post. Using a torque wrench and 10mm socket, tighten the battery terminal bolt to specification. Ensure the connection is snug but do not exceed the specified torque to avoid damaging the terminal.
   ⚠Do not overtighten the battery terminal bolt as this can crack the battery post or strip the threads.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Ensure all fuse box clips are fully engaged and the cover is secure
2. Verify the battery terminal is tight and the cable cannot be moved by hand
3. Reset the clock and radio presets as needed
4. Initialize power windows by fully opening and closing each window while holding the switch for 2 seconds in each position

Verification

• Turn the ignition to the ON position (do not start). Verify that the check engine light illuminates briefly then turns off, indicating proper ECM power
• Start the engine and confirm it starts normally without hesitation or unusual behavior
• Allow the engine to idle for 1-2 minutes and verify smooth operation with no warning lights
• Test engine responsiveness by briefly revving the engine to ensure proper fuel injection system operation
• Turn off the engine and restart it to confirm consistent starting performance

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