This procedure covers the replacement of the main relay (EFI relay) in the under-hood fuse/relay box of a 2014-2019 Toyota Corolla with the 1.8L I4 engine.

Warnings

Tools required

Parts

• Main EFI relay × 1 — Use OEM specification (Toyota 90987-02022 or equivalent)

Preparation

1. Park vehicle on level ground and apply parking brake
2. Turn ignition OFF and remove key from vehicle
3. Open hood and secure with prop rod
4. Allow engine to cool if recently operated

Procedure

1. 1

   Disconnect 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 3 minutes for residual electrical systems to discharge.
   Torque spec

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

   Locate the engine compartment fuse/relay box
   The main fuse/relay 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 fuse box cover
   Release the clips on the sides of the fuse box cover by pressing inward and lifting up. Remove the cover completely to access the relays. The relay diagram is typically printed on the underside of the cover - note the location of the EFI MAIN relay before proceeding.
4. 4

   Identify the main EFI relay
   Locate the main EFI relay in the fuse box. It is typically a larger relay in the upper section of the relay box, often marked as 'EFI MAIN' or 'EFI'. Verify against the diagram on the fuse box cover. On 2014-2019 Corollas, this is usually a black relay in position closest to the firewall.
5. 5

   Remove the old main relay
   Firmly grasp the relay body and pull straight upward with steady pressure. The relay should release from its socket. If resistance is encountered, use a relay puller or gently rock the relay side-to-side while pulling upward. Do not use excessive force or twist the relay.
6. 6

   Inspect relay socket
   Examine the relay socket terminals for corrosion, burning, or damage. Check for bent pins that may prevent proper contact. If corrosion is present, clean terminals with electrical contact cleaner and allow to dry. If terminals are burned or damaged, the entire fuse box may require replacement.
7. 7

   Install new main relay
   Align the new relay with the socket, ensuring the orientation matches the removed relay (relays are keyed and will only fit one way). Press the relay firmly into the socket until it seats completely and is flush with surrounding relays. Verify the relay is fully inserted and cannot be pulled out easily.
8. 8

   Reinstall fuse box cover
   Position the fuse box cover over the relay box, ensuring all clips align properly. Press down firmly on all edges until the clips engage with an audible click. Verify the cover is secure and seated properly.
9. 9

   Reconnect battery negative terminal
   Place the negative battery cable onto the negative battery post. Thread the terminal bolt by hand first to ensure proper alignment, then tighten to specification using a 10mm socket and torque wrench. Ensure the connection is secure but do not exceed specified torque.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Ensure fuse box cover is properly seated and all clips are engaged
2. Verify battery terminal is tight and cannot rotate on the post
3. Close hood and ensure it latches properly

Verification

• Turn ignition to ON position (do not start) and verify dash lights illuminate normally
• Listen for fuel pump prime (2-second whirring sound from rear of vehicle when ignition turned ON)
• Start the engine and verify it cranks and starts normally without hesitation
• Check for any warning lights on the instrument cluster that were not present before
• Verify all electrical systems function properly (windows, radio, climate control)
• Turn engine OFF, wait 10 seconds, and restart to confirm relay function is consistent

More procedures for this vehicle