2005 Honda Pilot Fuel Pump Relay Location: Your Essential Guide

Finding the fuel pump relay in your 2005 Honda Pilot is critical if you suspect fuel delivery problems like cranking but no start. This vital relay resides in the Under-Hood Fuse/Relay Box, specifically in position #5 (often clearly labeled "FUEL PUMP" or "FP"), located on the right (passenger) side of the engine compartment near the battery.

That's the key takeaway. When your Pilot isn't getting fuel due to a potential relay failure, knowing exactly where to find component R5 (FUEL PUMP) in the engine bay fuse box is the first essential step towards diagnosis or replacement. Now, let's break down all the details you need to access, identify, and handle this component confidently.

The Critical Role of the Fuel Pump Relay

Before diving under the hood, understanding why this relay matters is essential. Your Honda Pilot's electric fuel pump sits inside the fuel tank. When you turn the ignition key to "ON" (or press the start button without pressing the brake/clutch on later models), a signal is sent for just a few seconds to prime the fuel system. The component responsible for switching the high electrical current needed by the fuel pump on and off based on signals from the Powertrain Control Module (PCM - the engine computer) is the fuel pump relay. It acts as a heavy-duty electrically controlled switch. A failed relay often means the pump receives no power, resulting in a no-start condition even if the pump itself is perfectly healthy. Symptoms pointing towards a possible relay (or circuit) failure include the engine cranking normally but never actually starting, especially after the vehicle has been sitting, or a sudden inability to start after driving.

Precise Location: Under-Hood Fuse/Relay Box, Slot #5

For the 2005 Honda Pilot, the only location for the fuel pump relay is within the Under-Hood Fuse/Relay Box. Do not look inside the cabin at the interior fuse panel near your knees – that panel houses fuses and relays for accessories like the radio, interior lights, or power windows, but not the crucial engine management components like the fuel pump.

  • Physical Location: Open the hood and locate the battery on the passenger side (right-hand side when facing the windshield) of the engine compartment. Directly beside or slightly behind the battery, you'll find a black, rectangular plastic box. This is the Under-Hood Fuse/Relay Box. It has a removable lid.
  • Identifying the Lid: The lid might be labeled something like "FUSE/RELAY BOX ENGINE COMPARTMENT." It will have a diagram showing the layout and function of each fuse and relay slot inside. Finding this diagram is crucial for certainty.
  • Finding Slot #5: Carefully remove the lid. Look for a diagram printed directly on the lid's underside or molded into the plastic surface near the lid base. The relay positions are typically numbered. You are specifically looking for slot number 5. This slot should almost always be clearly labeled next to the diagram position as "FUEL PUMP" or abbreviated as "FP".
  • Appearance of the Relay: The relay itself is a small, square-ish black plastic cube (roughly 1 inch / 2.5 cm wide and long, and about 0.75 inches / 2 cm tall). It has 4 or 5 metal terminal prongs extending from the bottom that plug into the fuse box sockets. Compared to the larger standard fuses (mini or blade fuses), it looks chunkier. Compared to the even larger starter relay (if present in the same box), it is significantly smaller. Its physical designation within Honda's part system is often referred to as R5 when referencing that specific fuse box location.

Before You Start: Essential Tools & Safety

Safety is paramount when working with electrical components near the battery. Gather these simple tools and follow these precautions:

  • Tools Needed:
    • Your fingers (often sufficient for pulling the relay). Optional: Needle nose pliers with tape on the jaws (for cushioning) can help grip if the relay is tight. Avoid using large pliers that could damage surrounding fuses.
    • Small flat-blade screwdriver (may help with fuse box lid clips if needed).
  • Safety Procedures:
    • Turn the Engine Off: Ensure the ignition is completely off and the key is removed.
    • Disconnect the Battery: THIS IS HIGHLY RECOMMENDED. Disconnect the NEGATIVE (-) battery terminal first (the black cable). This reduces the risk of accidental short circuits while handling relays and fuses, which can damage components or blow fuses. Secure the cable away from the terminal. While often done without disconnecting the battery in practice for just relay swapping, disconnecting is the safest procedure.
    • No Smoking/Open Flames: The under-hood area is near fuel lines and the battery. Never introduce sparks or flames.
    • Work in Good Light: Ensure you can see clearly to avoid mishandling components.
    • Replace Correctly: Pay close attention to the relay's orientation when removing it and when inserting the new one. It will only fit one way due to its pin configuration. Forcing it can bend pins and damage the fuse box socket. The diagram on the lid might also show orientation. A common relay type used is the standard 5-pin automotive mini ISO relay.

Step-by-Step: Accessing and Removing the Relay

Follow these specific steps for the 2005 Pilot:

  1. Park Safely: Ensure the vehicle is parked on a level surface with the parking brake engaged.
  2. Open Hood: Release the hood latch and secure the hood with the prop rod.
  3. Identify Box: Locate the black Under-Hood Fuse/Relay Box on the passenger side near the battery.
  4. Remove Lid: Locate the securing clips or tabs on the lid. They are usually on the ends. Press the clips and lift the lid straight upwards. Place the lid aside where it won't get stepped on or blow away. Important: Locate the diagram on the lid showing position #5 (FUEL PUMP / FP).
  5. Visually Identify Relay #5: Visually confirm the relay in slot #5 matches the diagram position and label. Count positions carefully if labeling isn't clear. On the bottom row, it's the fifth slot from the driver's side edge or the second slot from the passenger side edge. Using the physical location relative to labeled neighbors can also help.
  6. Grip and Pull: Position your fingers squarely on top of the relay, applying even pressure downwards and then pull firmly straight upwards. If the relay feels stuck, using needle nose pliers gently on the top edges can provide more leverage. DO NOT pry the relay out from the sides with a screwdriver, as this risks damaging the fuse box socket. A firm, straight pull is key.
  7. Inspect: With the relay removed, take a moment to visually inspect the exposed pins in the fuse box slot #5 for any signs of corrosion, melting, or debris. Also, inspect the relay terminals themselves for similar damage or excessive heat signs (discoloration, warping).

Testing and Confirmation (The Wiggle/Click Test & Swap Method)

  • Basic Function Check:

    • "Click" Test: Have an assistant turn the ignition key to the "ON" (Run) position while you hold the relay near your ear. You should feel and hear a distinct "click" from the relay within the first 1-2 seconds as it primes the fuel pump. If there is no click at all, the relay or its controlling circuit is faulty.
    • "Wiggle" Test: With the ignition ON, gently wiggle the relay while it is fully seated in its socket. If you hear the fuel pump start whirring (located under the rear seat) or the engine suddenly starts, it indicates a poor connection or intermittent relay failure.

  • The Swap Method (Recommended for DIY): The most practical and reliable way for a DIYer to confirm a bad fuel pump relay in the 2005 Pilot is to swap it with an identical relay known to work from another location in the same Under-Hood Fuse/Relay Box. The most commonly used relay in modern vehicles like the Pilot is the standard 5-pin mini ISO relay. Other non-critical functions often use this exact same relay type.

    • Identify a Swap Candidate: Common suitable swap relays in the same box include the Radiator Fan Control Relay (sometimes labeled "FAN"), the Main Relay (often the largest relay, but confirm function first – avoid ignition/starter main relays as swap partners unless identical), or the A/C Compressor Clutch Relay (often labeled "A/C"). Consult your fuse box lid diagram! Important: Only swap with a relay that has the exact same physical shape and number of pins (typically 5 pins). Confirm they look identical. The part number molded on the relay (e.g., the common Honda relay number 38500-S9A-A01 or similar) will also be identical if it's the same spec relay.
    • Perform the Swap: Remove the known working relay (candidate relay). Carefully install it into the original fuel pump relay slot #5. Reinstall the removed (suspected bad) fuel pump relay into the slot where you took the candidate relay from. The diagram on the lid should accurately reflect the function of each slot even after swapping.
    • Test: Turn the ignition to ON. Listen carefully near the fuel tank filler neck or under the rear seat for the fuel pump's brief (2-3 second) priming whirring/humming sound. If you now hear the pump prime with the swapped relay in slot #5, your original fuel pump relay is likely bad. If you still do NOT hear the pump, the problem could be elsewhere (like the pump itself, fuse, wiring, inertia switch, or PCM issue), but you've effectively ruled out the relay as the culprit. Note that this test confirms relay function, not necessarily the pump's full capability to build pressure.

Reinstallation & Final Steps

  1. Install Correct Relay: Whether replacing a relay confirmed to be faulty or putting a good one back, ensure it's the appropriate relay. The orientation matters - the pins are keyed to fit one way only. Align the relay over the socket and press down firmly and evenly until it seats fully. You should feel or hear it click into place. Do not force it.
  2. Reinstall Lid: Position the lid over the fuse box. Align any tabs or hooks at one end and press down firmly until the retaining clips snap securely into place around the entire perimeter.
  3. Reconnect Battery: Reattach the NEGATIVE (-) battery cable first and tighten the clamp securely.
  4. Test: Turn the ignition to ON - you should hear the fuel pump prime (click & whirr near the tank for 1-2 seconds). If confirmed functional relay was installed and the pump primes, attempt to start the engine. The engine starting and running confirms the circuit, relay, and pump are operational at least for startup.
  5. Potential Trouble Codes: If the problem involved the relay circuit being open or shorted, the PCM might have stored a diagnostic trouble code (DTC) like P0230 (Fuel Pump Primary Circuit Malfunction). Using an OBD-II scanner to read and clear codes after repair is good practice.

Alternative Causes and Next Steps

While locating and checking the fuel pump relay is often the first step for a no-fuel condition, understand that other issues can mimic a bad relay:

  1. Blown Fuel Pump Fuse: The fuel pump circuit has a primary fuse protecting it. Check fuse #42 (15A) in the Under-Hood Fuse/Relay Box (refer to the lid diagram). This fuse is essential even if the relay is working. A multimeter is the best tool for this check.
  2. Faulty Fuel Pump: The pump itself can fail due to wear, contamination, or running the tank consistently low causing overheating. Confirming relay power delivery is the first step before condemning the pump. Pressure testing at the fuel rail or listening for pump activation is needed.
  3. Fuel Pump Inertia Switch: Designed to cut fuel pump power in a collision. Though rare to trip accidentally in a Pilot, it can be checked and reset (usually located in the passenger footwell near the kick panel or sometimes under the driver's seat – consult your manual). Look for a prominent red reset button on a small device mounted low near the firewall.
  4. Ignition Switch Problems: Faults in the ignition switch can prevent the signal for relay activation from the PCM. Symptoms might include other accessories acting strange.
  5. Wiring Harness Issues: Damage, corrosion, or shorts in the wiring between the battery, fuse, relay, pump, PCM, and ground points. Inspect visible harnesses, especially around the fuse box and fuel pump access area near the tank. Check ground points like the one near the battery negative terminal.
  6. PCM Fault: A rare but possible cause would be the engine computer failing to send the activation signal to the relay. Diagnosing this requires expertise.

Finding the Correct Replacement Relay

If your tests confirm the relay is faulty, replacing it is straightforward:

  • OEM (Original Equipment Manufacturer): Purchase from a Honda dealer (parts department). Provide your VIN to ensure getting the exact correct relay part number (e.g., 38500-S9A-A01 is a common Honda relay type used in that era). This guarantees compatibility.
  • High-Quality Aftermarket: Reputable brands like Denso, Standard Motor Products (SMP), Niehoff, BWD, or ACDelco offer reliable replacements. Search for "2005 Honda Pilot Fuel Pump Relay" or use the part number found on your old relay.
  • Confirm Specifications: Ensure the replacement is a 5-pin SPST (Single Pole Single Throw) or SPDT (Single Pole Double Throw) automotive mini ISO relay rated for the amperage (usually 20-30 Amp). Physical appearance (size, pin layout) must match exactly. The terminal pattern is industry standard for mini ISO relays.

The Critical Starting Point

Knowing precisely that the 2005 Honda Pilot fuel pump relay (component R5) resides in the #5 position of the engine compartment Under-Hood Fuse/Relay Box, near the battery, gives you the power to address one of the most common causes of a no-start condition efficiently. Following the steps outlined for access, identification, testing (especially the practical swap method), and replacement puts this potential problem firmly within the scope of a capable DIY owner. Remember, safety precautions like battery disconnection are crucial. If testing points beyond a simple relay failure, don't hesitate to seek assistance from a qualified Honda technician for advanced diagnostics involving wiring, pump function, or PCM signals.

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