2004 Honda Odyssey Fuel Pump Relay: Location, Symptoms, and Replacement Guide

If you own a 2004 Honda Odyssey and your vehicle won't start, stalls after starting, or has intermittent starting issues, the fuel pump relay is likely the culprit. The fuel pump relay on a 2004 Honda Odyssey is most commonly found in the engine bay fuse/relay box near the battery, but some configurations place it in the interior fuse box behind the glove box on the passenger side. This guide will walk you through exactly where to find it, how to test it, and what to do if it's faulty.

Where Is the Fuel Pump Relay Located?

The 2004 Honda Odyssey has two primary locations where the fuel pump relay can be found:

1. Engine Bay Fuse/Relay Box (Most Common)
The primary under-hood fuse box is located in the back of the engine compartment on the passenger's side, near the battery. Open the fuse box cover and look at the diagram printed on the inside. The fuel pump relay is often labeled "FP," "FUEL PUMP," or "PUMP." If you are unsure, you can swap it with an identical relay from the same box to test if the fuel pump circuit is activated.

2. Interior Fuse Box Behind the Glove Box
If you cannot find the relay in the engine bay, check the interior fuse box. On the 2004 Odyssey, the passenger compartment fuse boxes are located underneath the dashboard on both the driver's and passenger's side. The interior fuse box behind the glove box is a secondary location where some builds place the relay. Remove the glove box or the kick panel and check the lid diagram for the same "FP" or "FUEL PUMP" label.

3. Driver's Side Under-Dash Fuse Box
According to multiple sources, the fuel pump relay on some 2004 Honda Odyssey models is located in the driver's side under-dash fuse box. One source describes it as a blue, rectangular relay located on the fuse box above the driver's left foot. You need to remove the trim panel (the one near the sunroof switch area) to access it. The fuse box diagram for the driver's side shows a 15A fuse for the fuel pump.

Symptoms of a Failing Fuel Pump Relay

A faulty fuel pump relay can cause several noticeable problems. If you experience any of these, start by checking the relay:

  • The vehicle won't start: The most common symptom. The engine may crank but never fire up because the fuel pump is not receiving power.
  • Intermittent starting: The car starts sometimes but not others, indicating an intermittent electrical connection within the relay.
  • Engine dies after starting: The engine may start briefly but then stall out shortly after, as the relay fails to maintain power to the fuel pump.
  • No noise from the fuel pump: When you turn the ignition key to the "ON" position (before cranking), you should hear a brief whirring sound from the fuel pump located near the rear of the vehicle. If you don't hear it, the relay or pump may be faulty.

How to Test the Fuel Pump Relay

Before buying a new relay, you can test the existing one. Here are the steps:

  1. Locate the relay: Use the information above to find the correct relay in your fuse box.
  2. Visual inspection: Remove the relay and check for any signs of corrosion, burns, or melted plastic.
  3. Swap test: The easiest way to test is to swap the fuel pump relay with a relay of the same size and rating from another part of the fuse box (like the horn or cooling fan relay). If the car starts after the swap, the original relay is faulty.
  4. Multimeter test: If you have a multimeter, you can test the relay's coil resistance and check for continuity across the switch terminals when power is applied. A faulty relay will show no continuity or have an incorrect resistance reading.

What to Do If the Relay Is Faulty

If you have confirmed the fuel pump relay is the problem, replace it with a new one. The genuine Honda part numbers for the 2004 Odyssey include 39794-SDA-004 and 39794-SDA-A03. Make sure to purchase a relay that matches your vehicle's specifications. Also, check the associated fuse (the 15A "Fuel Pump" fuse in the driver's side fuse box) to ensure it is not blown.

Why the Fuel Pump Relay Fails

The fuel pump relay in the 2004 Honda Odyssey can fail for several reasons:

  • Current overload: If the fuel pump draws more current than the relay is designed to handle, the relay contacts can overheat and burn out.
  • Short circuit: A short in the electrical system can cause a sudden current overload, damaging the relay's coil or contacts.
  • Age and wear: Over time, the internal components (electromagnetic coil and mechanical contacts) can wear out due to repeated use, vibrations, and heat.

Upgrading Your Fuel Pump: The KEMSO Solution

If you have replaced the fuel pump relay and still experience fuel delivery issues, the problem may be the fuel pump itself. For a reliable, high-performance replacement, we recommend the KEMSO Fuel Pump. KEMSO fuel pumps are built to exceed OEM specifications, offering a direct bolt-on installation with no modifications required. Each pump is a high-performance, OEM replacement unit backed by a lifetime warranty, giving you confidence on every drive. Whether you are commuting or taking a road trip, a KEMSO fuel pump ensures consistent fuel delivery and long-lasting durability.

Visit KEMSO Racing today to find the perfect fuel pump for your 2004 Honda Odyssey: https://www.kemsoracing.com/

Final Thoughts

The fuel pump relay on a 2004 Honda Odyssey is easy to access and test. By following the steps above—checking the relay, fuses, and voltage—you can quickly determine whether the relay is the culprit or if the issue lies elsewhere in the fuel system. When replacement is needed, always use a quality relay that matches OEM specifications. And if the fuel pump itself is failing, upgrading to a KEMSO fuel pump provides peace of mind with its lifetime warranty and superior performance.

For more information on fuel pump replacements, diagnostics, and performance parts, visit https://www.kemsoracing.com/.


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