The 2004 Honda Pilot uses multiple relays rather than a single one, and they live in two fuse/relay boxes in the engine bay and inside the cabin. The fuel pump relay is typically located in the engine bay box, with other essential relays labeled on the lids.
Two fuse/relay boxes: engine bay and interior
For a 2004 Pilot, relays live in two main fuse/relay boxes. The engine bay box is mounted in the engine compartment, usually on the driver’s side near the firewall, and the interior box sits under the dash on the driver’s side. Each box has a diagram on its lid that labels each relay and fuse, so checking the diagram is your quickest way to identify a specific relay.
- Engine bay fuse/relay box — holds the major power relays for engine systems, including the fuel pump relay and typically the main relay. The lid diagram will indicate exact labels.
- Interior fuse box — houses relays related to cabin systems or secondary components, as labeled on the box lid. Not all models require an interior relay for essential engine functions, but some pilots do use relays here.
The diagram on the inside of each lid is your best guide. If you’re unsure about a particular relay, consult the owner’s manual or a factory fuse/relay diagram for your exact vehicle, as layouts can vary by market and production run.
In practice, many owners start with the fuel pump relay when diagnosing running issues, since a faulty relay can cause no-start or stalling problems. Locating the right relay prepares you for testing, swapping, or replacing it as needed.
Common relays you might encounter
Below are the relays you’re most likely to find in a 2004 Pilot, along with what they control. Always confirm with the box lid or service manual for your exact vehicle since labels can vary by year and market.
- Fuel pump relay — powers the fuel pump; located in the engine bay fuse/relay box.
- Main relay — provides power to the engine control unit and other critical systems; typically in the engine bay box.
- Starter relay — energizes the starter solenoid; usually found in the engine bay box.
- A/C compressor relay — controls the air conditioning compressor clutch; engine bay.
- Cooling fan relay — controls radiator cooling fans; engine bay.
- Horn relay — may be located in the interior or engine bay fuse box depending on market; check the lid diagram.
Testing and identifying a faulty relay can be done by swapping with a known-good relay of the same type or using a multimeter to check coil resistance and contact continuity, but proceed with caution and disconnect power before handling relays to avoid shorts.
How to locate and test a relay: quick steps
Use these steps to locate and test a suspect relay on a 2004 Pilot. The goal is to confirm whether a vehicle issue is relay-related or something else in the electrical system.
- Open the appropriate fuse/relay box and locate the diagram on the lid to identify the relay you’re testing.
- Remove the suspected relay carefully by pulling straight up with a firm grip.
- To test, swap it with an identical spare relay from the same box; see if the problem follows the relay.
- If you must test electrically, use a multimeter to check coil resistance (note the spec on the diagram) and verify continuity across the switched contacts when the ECU energizes the coil.
- Reinstall the relay and reconnect power; clear any warning lights if applicable and test the system again.
If you’re unsure or the no-start/no-function persists after swapping relays, consider having a professional diagnose the electrical system to avoid misdiagnosis or damage.
Summary
Relays on a 2004 Honda Pilot are not located in a single spot. They reside in two fuse/relay boxes—one in the engine bay and one under the dash—each with lid diagrams that label every relay. The fuel pump relay is a common starting point, but other essential relays include the main relay, starter relay, A/C clutch relay, and cooling fan relays. Always consult the diagram on the box lids or the owner's manual to identify the exact relay for your vehicle and follow proper safety procedures when testing or replacing them.