2004 Honda Accord Fuel Pump Relay Location: Find & Fix Fast

The precise location of the fuel pump relay in your 2004 Honda Accord is within the main under-hood fuse and relay box, typically labeled as "Relay 2" (ECU, ECU/FP, or FP).

Finding the correct component quickly is essential when diagnosing suspected fuel pump relay issues. This guide provides detailed, step-by-step instructions to locate, identify, test, and replace the fuel pump relay in your 7th generation (2002-2006) Honda Accord, specifically the 2004 model year. Knowing the 2004 Honda Accord fuel pump relay location is the first step towards solving no-start or fuel delivery problems.

Where the Under-Hood Fuse/Relay Box is Located

Open your Honda Accord's hood. Locate the black, rectangular plastic box on the driver's side of the engine compartment, near the strut tower (the large suspension component connecting the body to the wheel assembly). This is the primary under-hood fuse and relay box. It is easily accessible and houses numerous fuses and several relays responsible for critical vehicle functions. Unlike some vehicles where components might be scattered, Honda consolidates primary electrical controls here for easier access during diagnostics and maintenance tasks. The lid usually secures with plastic clips on the sides.

Identifying the Specific Fuel Pump Relay (Relay 2)

  1. Remove the Box Cover: Press down on the securing clips located on the left and right sides of the lid simultaneously and lift the cover straight up. Set it aside carefully.
  2. Locate the Relay Diagram: Look for a diagram printed inside the lid or directly on the surface of the fuse box itself. This diagram is your essential map, detailing the layout and function of every fuse and relay housed within. Locating this diagram is crucial for correct identification.
  3. Find "Relay 2" or Equivalent Label: Search the diagram for the slot labeled "Relay 2", "ECU", "ECU/FP", or "FP". This designation specifically refers to the relay controlling the Engine Control Unit (ECU) and/or the Fuel Pump. In the context of the fuel pump circuit, this relay provides primary power. While most 2004 Accords use "Relay 2" for the ECU/Fuel Pump function, always verify using the specific diagram unique to your vehicle's fuse box.
  4. Physical Identification: Within the box, find the relay socket corresponding to the diagram location for "Relay 2". Confirm it's a standard ISO Micro Relay, roughly cube-shaped (about 1 inch or 25mm on each side), commonly black or gray plastic. It will have four or five electrical terminals protruding from the bottom.
  5. Terminal Wire Color Confirmation (Advanced): For definitive confirmation, carefully unplug the relay if necessary for testing/replacement and note the wire colors on the socket. The fuel pump relay output wire (terminal facing away from the clip) is typically Yellow with a Black tracer (YEL/BLK). This wire runs directly to the fuel pump. Finding this wire provides the most accurate confirmation you have the correct relay.

Recognizing Fuel Pump Relay Failure Symptoms

Knowing the 2004 Honda Accord fuel pump relay location is essential because a failing relay often mimics a dead fuel pump. Key symptoms include:

  • Engine Cranks but Won't Start: This is the most common indicator. The starter motor turns the engine, but no fuel is delivered to the cylinders.
  • No Fuel Pump Prime Sound: When you turn the ignition key to the "ON" (RUN) position (without cranking the engine), you should normally hear a distinct, low humming sound from the rear of the car (near the fuel tank) lasting about 2 seconds. This is the fuel pump pressurizing the system. The absence of this sound strongly points towards a relay, fuse, or pump issue.
  • Intermittent Starting Problems: The vehicle might start sometimes but fail other times, often without warning, especially when the engine or engine bay is hot. Heat can exacerbate failing relay contacts.
  • Engine Stalling While Driving: A relay on the verge of complete failure might intermittently cut power to the fuel pump during operation, causing sudden engine stalls. This is a serious safety concern.
  • No Power to Fuel Pump: Diagnostically, confirming a lack of power at the fuel pump connector (located near or on top of the fuel tank) when the ignition is cycled, while battery voltage is present at the relay's input terminal, strongly points to the relay or fuse.

Testing the 2004 Honda Accord Fuel Pump Relay

Before replacing parts, testing is prudent. Relays can be tested while installed (operational test) or removed (bench test). Always disconnect the negative battery terminal before handling relays or fuses to prevent electrical shorts.

  1. Operational 'Click' Test:

    • Locate the relay per the instructions above.
    • Have an assistant turn the ignition key to the "ON" (RUN) position.
    • Place your finger lightly on the relay. You should feel and possibly hear a distinct "click" within the relay housing as it energizes.
    • After about 2 seconds, your assistant should turn the ignition off, and you should feel another "click" as the relay de-energizes. Feel for both clicks. If you only hear/felt one click, or none at all, the relay might be faulty. If felt, proceed to voltage test.

  2. Power Input and Output Voltage Test: Requires a multimeter.

    • Set multimeter to DC Volts (~20V range).
    • Locate the relay's input terminal (typically a Yellow wire or BLK/YEL wire – power directly from battery via fuse). Carefully backprobe the wire connector (pierce insulation slightly or probe exposed terminal back) with the multimeter's red probe. Black probe to bare metal ground (chassis). With key ON, you should read battery voltage (~12V). If not, check the under-hood main fuse (labeled MAIN or BATTERY) and the No. 46 (15A) fuse in the under-hood box.
    • Locate the relay's output terminal (typically YEL/BLK wire going to the fuel pump). Backprobe this terminal. Have assistant turn key ON. You should see battery voltage for about 2 seconds. If you have input power but NO output power when the key is cycled, the relay is very likely faulty.

  3. Bench Testing: Removing and testing continuity across terminals with a multimeter confirms internal function. See relay diagrams for terminal activation.

Replacing the Faulty Fuel Pump Relay

Once a faulty relay is confirmed:

  1. Purchase the Correct Replacement: Ensure you get a standard ISO Micro Relay. While Honda Genuine parts are ideal (Part# 38501-S0A-A02, though superseded numbers exist), high-quality equivalents from automotive electrical suppliers (Tyco, Omron, Bosch, Denso, Hella, etc.) are also reliable. Avoid the cheapest non-branded options. Take your old relay to the parts store for visual matching.
  2. Safety First:
    • Turn the ignition OFF.
    • Disconnect the NEGATIVE (-) battery cable.
    • Ensure you are not generating static electricity (touch metal bodywork).
  3. Access: Open hood, unclip and remove the under-hood fuse box cover as before.
  4. Removal: Firmly grasp the fuel pump relay installed in the "Relay 2" slot. Pull it straight up and out of its socket. Do not twist or yank excessively sideways.
  5. Installation: Orient the new relay correctly (it usually has a faint mold marking on top indicating pin 1). The relay will only fit one way due to asymmetrical terminal spacing and a locating tab. Align the terminals and carefully push the relay straight down into the socket until it seats firmly. You should feel it click into place. Avoid forcing it. Ensure it's fully seated and level with the surrounding relays.
  6. Reassemble: Replace the fuse box cover securely, ensuring the clips engage properly.
  7. Reconnect Battery: Reattach the negative battery terminal.

Crucial Safety and Diagnostic Tips

  • Check Fuses FIRST: Before concluding the relay is bad, always check the two critical fuses: The large Main Fuse (BATTERY fuse, 100A) and the Fuel Pump Fuse (No. 46, 15A), both located in the under-hood box. A blown fuse is often the cause and much simpler to replace. Find them using the diagram inside the fuse box lid.
  • Fuel Pump Health: A failed fuel pump or faulty wiring between the relay and pump can also cause symptoms. Testing for power at the fuel pump connector after confirming the relay and fuses are good is the next diagnostic step.
  • No Sparks:Never probe or test electrical components with fuel spills present or if fuel lines are disconnected. Gasoline vapors are extremely flammable. Ensure good ventilation in the work area.
  • Static Electricity: Static discharge can damage the ECU. Before handling the relay or other sensitive electronics, discharge yourself by touching bare metal on the car's body (door striker plate, engine bracket).
  • Terminal Care: Be gentle when removing and installing relays. Avoid bending the relay terminals or damaging the fragile pins inside the fuse box socket. Damaged sockets require professional repair.
  • Depressurizing: While not strictly required for relay replacement itself, any work involving fuel lines near the pump requires depressurizing the fuel system to prevent gasoline spray. Consult your service manual for the proper procedure.

Conclusion: Empowering Your Accord Repair

Pinpointing the 2004 Honda Accord fuel pump relay location inside the driver's side under-hood fuse box ("Relay 2") is a manageable task crucial for diagnosing common no-start conditions. By following this guide – accessing the box, using the diagram to identify the relay, understanding failure symptoms, performing basic tests, and safely replacing the component – you can effectively address this frequent failure point. Remember to prioritize safety, always check the associated fuses first (Main and No. 46), and confirm diagnosis with voltage tests whenever possible. Solving this issue yourself restores your Accord's reliability and avoids potentially high labor costs at a repair shop.

Back to blog