This procedure covers the removal and replacement of a relay in the under-hood or interior fuse/relay box on a 2016-2021 Honda Civic with the 1.5L turbo engine.

Warnings

Tools required

Parts

• Relay (matching specific circuit number) × 1 — Use OEM specification based on relay box diagram

Preparation

1. Turn the ignition to OFF and remove the key
2. Identify which relay needs replacement by referring to the fuse/relay box diagram (under-hood box on driver's side or interior box under dashboard)
3. For under-hood relay replacement, open the hood and secure with prop rod
4. If replacing an interior relay and battery disconnect is desired for safety, disconnect the negative battery terminal

Procedure

1. 1

   Access the relay box
   Locate the appropriate relay box. For under-hood relays, release the cover clips by pressing the tabs on each side and lift the cover off. For interior relays (passenger side lower dash), press the release tabs and pull the panel down to access the fuse/relay box.
2. 2

   Identify the target relay
   Consult the relay diagram printed on the inside of the fuse box cover or in the owner's manual. Relays are typically larger than fuses and have 4-5 pins. Common relays include fuel pump, headlight, A/C compressor, and horn relays. Note the relay number and location.
3. 3

   Remove the relay
   Grasp the relay firmly and pull straight up with steady pressure. If the relay is difficult to remove, use needle-nose pliers to grip the relay body (not the pins) and rock gently side-to-side while pulling upward. Some relays have a small tab that can be lifted with a flathead screwdriver to assist removal.
4. 4

   Inspect the relay socket
   Examine the relay socket terminals for corrosion, damage, or debris. If corrosion is present, clean terminals with electrical contact cleaner and a small wire brush. Check for any bent pins in the socket and straighten if necessary using needle-nose pliers.
5. 5

   Install the new relay
   Verify the new relay matches the part number and configuration of the old relay. Align the relay pins with the socket, ensuring correct orientation (relays typically have an alignment key or notch). Press the relay firmly into the socket until it seats completely and sits flush with adjacent relays.
   ⚠Installing the wrong relay type can cause electrical system malfunction or component damage. Verify part number match before installation.
6. 6

   Reinstall the relay box cover
   Position the relay box cover over the box, ensuring the relay diagram faces outward for future reference. Press down on all corners until the retaining clips click into place and the cover is secure.
7. 7

   Reconnect battery if disconnected
   If the battery was disconnected, reconnect the negative battery terminal and tighten the terminal bolt to specification. Ensure the terminal connection is clean and secure.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Ensure the relay box cover is properly secured with all clips engaged
2. If battery was disconnected, reset the clock and radio presets as needed
3. Close the hood if working in the engine compartment and ensure it latches securely

Verification

• Turn the ignition to ON (engine off) and verify the electrical system controlled by the relay functions properly
• For fuel pump relay, listen for the fuel pump prime (2-second hum) when ignition is turned on
• For headlight relay, test headlight operation in both low and high beam modes
• For A/C compressor relay, turn on the A/C and verify compressor engages (engine running)
• Check for any warning lights on the instrument cluster that may indicate electrical issues
• Start the engine and verify normal operation with no unusual behavior from the affected system

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