2004 Toyota Highlander Fuel Pump Relay Location: Complete Guide for DIY Owners

The fuel pump relay on a 2004 Toyota Highlander is located inside the engine compartment fuse box (also called the under-hood relay block), which sits on the driver's side near the battery. Specifically, it is the second relay from the front of the vehicle in the smaller relay row, and it is often labeled as "FUEL PUMP" or "FUEL OPN" on the fuse box cover diagram. This relay controls power delivery to the fuel pump, and when it fails, the engine may crank but not start. Understanding exactly where it is and how to test it can save you time and money before assuming the fuel pump itself is bad.

Why the Fuel Pump Relay Matters on Your 2004 Highlander

The fuel pump relay acts as an electrical switch. When you turn the key to the "ON" position, the engine control module (ECM) sends a signal to the relay, which then closes and sends battery voltage to the fuel pump. Without a working relay, the fuel pump never gets power, and your Highlander won't start no matter how much gas is in the tank.

On the 2004 model, which is part of the first generation (2001–2007), the fuel system is designed to shut off the pump automatically in a collision via an inertia switch, but the relay remains the primary control point. A bad relay is a common failure point and is much cheaper and easier to replace than the actual fuel pump.

Exact Location of the Fuel Pump Relay: Step-by-Step

Step 1: Open the Hood

Park your Highlander on a level surface, engage the parking brake, and pop the hood. The engine compartment fuse box is clearly visible on the driver's side, just behind the headlight assembly and next to the air cleaner housing.

Step 2: Remove the Fuse Box Cover

Press the two retaining clips on the sides of the fuse box cover and lift it straight off. On the underside of the cover, you will find a diagram that labels each fuse and relay. Look for a relay labeled "FUEL PUMP" or "FUEL OPN." In many 2004 Highlanders, the relay is marked with a fuel pump icon or the abbreviation "F/P."

Step 3: Identify the Correct Relay

The fuse box contains two rows of relays. The fuel pump relay is typically the second relay from the front of the vehicle in the smaller row closest to the fender. It is a standard four-pin relay, usually gray or black in color. If you are unsure, consult the diagram on the cover or refer to your owner's manual.

Step 4: Visual Confirmation

Once you locate the relay, gently pull it straight out using your fingers or a small relay puller tool. The relay should come out without excessive force. Compare it to other relays in the box – they should all look similar in size and pin configuration.

How the Fuse Box is Organized

The engine compartment fuse box on the 2004 Highlander contains both fuses and relays. The main fuses are arranged in a grid pattern, while the relays sit in a separate row typically on the right side of the box (when facing the vehicle from the front).

Key fuses related to the fuel system include:

  • Fuel Pump Fuse (15A or 20A) – This fuse protects the fuel pump circuit. It is usually located in the same fuse box, often labeled "FUEL PUMP" or "EFI." Check this fuse first before replacing the relay.
  • EFI Fuse (15A) – This fuse powers the engine control module and fuel injection system. A blown EFI fuse can also cause a no-start condition.

Important: Always disconnect the battery negative terminal before working on the fuse box to avoid short circuits.

Testing the Fuel Pump Relay: Determine if It's Actually Bad

Before buying a new relay, you can test the old one with a simple multimeter. Here is a step-by-step procedure that any DIY owner can follow.

What You Need:

  • Digital multimeter (set to ohms or continuity mode)
  • 12V battery or car battery
  • Small jumper wires (optional)

Procedure:

  1. Remove the relay from the fuse box.
  2. Identify the relay pins. A standard four-pin relay has two pins for the coil (usually pins 85 and 86) and two pins for the switch (usually pins 87 and 30). The diagram on the relay housing typically shows the pin layout.
  3. Test the coil resistance. Place the multimeter probes on pins 85 and 86. You should read a resistance between 50 and 120 ohms. If the reading is infinite (open circuit), the coil is burned out and the relay is bad.
  4. Test the switch contacts. With the relay removed, place the probes on pins 87 and 30. You should read infinite resistance (no continuity) because the switch is normally open.
  5. Apply 12V to the coil. Connect a 12V source across pins 85 and 86 (positive to 85, negative to 86). You should hear a distinct clicking sound as the switch closes.
  6. Re-test the switch. While the coil is energized, place the probes on pins 87 and 30 again. You should now read near-zero resistance (continuity). If the switch does not close when power is applied, the relay is defective.

If the relay clicks but the switch does not show continuity, the internal contacts are burned or pitted, and the relay needs replacement.

Common Symptoms of a Bad Fuel Pump Relay

Knowing the symptoms helps you diagnose the issue quickly. Here are the most common signs that the fuel pump relay on your 2004 Highlander is failing:

  1. Engine cranks but does not start. This is the #1 symptom. You turn the key, the starter engages, but the engine never fires up because no fuel is reaching the injectors.
  2. No fuel pump priming noise. When you turn the key to the "ON" position (before cranking), you should hear a brief whirring sound from the fuel pump for about 2–3 seconds. If you don't hear this sound, the relay or pump may be faulty.
  3. Engine starts then dies immediately. Sometimes a failing relay can briefly send power, but the contacts vibrate open once the engine starts, cutting fuel pressure.
  4. Intermittent stalling. If the relay contacts are dirty or weak, the pump may lose power while driving, causing the engine to stall suddenly. This is dangerous, especially at highway speeds.
  5. Check Engine Light (CEL) comes on. The ECM monitors the fuel pump circuit and may store diagnostic trouble codes (DTCs) like P0230 (Fuel Pump Primary Circuit Malfunction) or P0231 (Fuel Pump Secondary Circuit Low).

Note: These symptoms can also be caused by a blown fuel pump fuse, a bad fuel pump, or a failed ECM. Always test the relay first because it is the easiest part to check.

Replacement Part: What to Buy and How to Install

Where to Find the Relay

You can purchase a new fuel pump relay for your 2004 Toyota Highlander from several sources:

  • Toyota dealership – OEM part number is often 90987-02030 or similar. Expect to pay $20–$35.
  • Auto parts stores – Brands like Denso, Standard Motor Products, or BWD sell direct replacements for $10–$20.
  • Online retailers – Amazon, RockAuto, and other sites offer both OEM and aftermarket options.

Installation Steps

  1. Disconnect the battery negative terminal.
  2. Locate the relay as described above.
  3. Pull out the old relay straight up. Do not twist or pry it out with a screwdriver, as this can damage the fuse box terminals.
  4. Insert the new relay in the same orientation. Push down firmly until it clicks into place.
  5. Reconnect the battery and test by turning the key to "ON." Listen for the fuel pump priming noise, then start the engine.

Important: Never use a relay that has different pin spacing or amperage rating than the factory part. Using the wrong relay can cause electrical damage or a fire.

When the Relay Isn't the Problem: Next Steps

If you replace the relay and the Highlander still does not start, move on to these checks:

1. Check the fuel pump fuse. Locate the "FUEL PUMP" or "EFI" fuse in the same fuse box. Use a test light or multimeter to verify it is not blown. A blown fuse indicates a short circuit in the fuel pump wiring or the pump itself.

2. Test for power at the fuel pump connector. The fuel pump is located inside the fuel tank, accessible through a service panel under the rear seat or cargo area. With the relay installed and the key in the "ON" position, use a multimeter to check for 12V at the pump connector. If you have voltage but no pump operation, the pump is bad.

3. Check the inertia fuel shutoff (IFS) switch. The 2004 Highlander is equipped with an inertia switch that cuts power to the fuel pump in a collision. It is usually located under the dashboard on the passenger side or behind the kick panel. If it has tripped, reset it by pressing the button on top.

4. Inspect wiring and connectors. Corrosion or damage to the wiring harness between the relay and the fuel pump can cause intermittent or no power. Pay special attention to the connector at the fuel pump module on top of the tank.

Why the Fuse Box Diagram Matters

Having a clear fuse box diagram for your 2004 Highlander is essential. The diagram tells you exactly which relay is for the fuel pump and which fuses are related. Without it, you could easily pull the wrong relay or fuse, wasting time.

You can find the diagram in several places:

  • Inside your owner's manual in the fuse section.
  • On the underside of the fuse box cover (most models have a printed diagram there).
  • Online resources like the ones linked in this article provide detailed diagrams for the 2004 model.

The fuse box for the 2004 Highlander is also shared with the Toyota Kluger, so diagrams for either vehicle are interchangeable.

Safety Precautions When Working with the Fuel System

1. Always work in a well-ventilated area. Gasoline vapors are highly flammable and can accumulate inside the engine compartment.

2. Disconnect the battery before removing any fuses or relays. This prevents accidental shorts and sparks.

3. Never bypass the relay with a jumper wire for testing unless you are absolutely sure of the circuit. Running the fuel pump continuously with the engine off can flood the engine or cause a fire.

4. If you smell gasoline, stop immediately. A fuel leak anywhere in the system is dangerous. Have the vehicle inspected by a professional.

5. Wear safety glasses. Gasoline can spray when disconnecting fuel lines or removing the pump module.

KEMSO Fuel Pump: The Best Replacement for Your 2004 Highlander

When the time comes to replace the actual fuel pump (not just the relay), choosing a high-quality replacement matters. The fuel pump is a critical component that must deliver consistent pressure and volume for the engine to run properly. A failing pump can cause hesitation, poor fuel economy, and even engine damage from lean running conditions.

KEMSO offers a line of high-performance aftermarket fuel pumps that are direct OEM replacements for your 2004 Toyota Highlander. These pumps are engineered to meet or exceed the original factory specifications, ensuring a perfect fit and reliable operation. Each KEMSO fuel pump is built with precision components and undergoes rigorous testing to deliver dependable performance in all driving conditions.

What sets KEMSO apart is their commitment to quality and customer satisfaction. Every KEMSO fuel pump comes with a lifetime warranty, giving you peace of mind that your investment is protected. Whether you are replacing a worn-out pump or upgrading for better reliability, KEMSO provides a cost-effective solution without sacrificing quality.

To see the full range of KEMSO fuel pumps and find the correct fit for your 2004 Highlander, visit their website at https://www.kemsoracing.com/. Their product lineup covers a wide variety of vehicles, including cars, motorcycles, and powersports applications, all backed by the same lifetime warranty. With KEMSO, you get a fuel pump that is built to last and supported by a company that stands behind its products.

Final Thoughts: Diagnose Smart, Replace Right

The fuel pump relay on a 2004 Toyota Highlander is located in the engine compartment fuse box on the driver's side. It is the second relay from the front in the smaller relay row, and it is clearly labeled on the fuse box cover diagram. Testing the relay with a multimeter takes less than 10 minutes and can save you from buying an expensive fuel pump you don't need.

If the relay tests good but the engine still won't start, check the fuel pump fuse, the inertia switch, and finally the fuel pump itself. When replacement is necessary, choose a high-quality part like KEMSO to ensure long-term reliability. A properly functioning fuel system is essential for your Highlander's performance and safety, so don't cut corners.

Remember: a simple $15 relay can stop a $30,000 SUV in its tracks. Knowing where it is and how to test it is one of the most valuable skills for any Highlander owner.

For the best replacement fuel pump for your 2004 Toyota Highlander, visit KEMSO Racing at https://www.kemsoracing.com/ and check out their lifetime warranty OEM replacement pumps.


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