2005 Scion tC Fuel Pump Relay: Location, Testing, and Replacement Guide

The fuel pump relay in your 2005 Scion tC is the small but critical component that controls power delivery to the electric fuel pump mounted inside the gas tank. When this relay fails, your engine may crank but refuse to start, or the car may stall while driving. The good news is that the relay is inexpensive, easy to test, and replacing it takes less than ten minutes with basic hand tools. This guide walks you through everything you need to know, from locating the relay in the engine bay to diagnosing a faulty unit and swapping in a new one.

Where Is the Fuel Pump Relay on a 2005 Scion tC?

The fuel pump relay on the 2005 Scion tC lives in the under-hood fuse and relay box, which sits on the driver's side of the engine bay near the battery. The relay box has a black plastic cover with a diagram printed on the underside. If the diagram has worn off, look for a rectangular component labeled "FUEL PUMP" or "EFI" (Electronic Fuel Injection). The relay itself is a small cube made of dark plastic with either four or five metal prongs on the bottom.

Some owners confuse the fuel pump relay with the EFI relay because they are identical in shape and sit side by side in the same fuse box. The fuel pump relay is usually the one closer to the fender, while the EFI relay sits closer to the engine. When in doubt, pull both out and check the part numbers stamped on the housing. They may be interchangeable for testing purposes.

Symptoms of a Bad Fuel Pump Relay in a 2005 Scion tC

Understanding the warning signs of a failing fuel pump relay can save you from being stranded. Here are the most common symptoms reported by Scion tC owners:

  1. Engine cranks but does not start. This is the most obvious sign. You turn the key, the starter motor spins the engine, but the fuel pump never receives power, so no fuel reaches the injectors.

  2. Car stalls while driving. If the relay fails intermittently, power to the fuel pump cuts out while the engine is running. The car will sputter, lose power, and die. After a few minutes, the relay cools down, and the car may restart.

  3. No whining sound from the fuel tank. When you turn the ignition key to the "ON" position (without cranking the engine), you should hear a brief whining or humming sound from the rear of the car. This is the fuel pump pressurizing the system. No sound means the pump is not receiving power, which points to a relay problem, a blown fuse, or a dead pump.

  4. Check Engine Light illuminates. A failed fuel pump relay can trigger diagnostic trouble codes related to fuel pressure or crankshaft position sensor correlation. Common codes include P0087 (Fuel Rail Pressure Too Low) and P0230 (Fuel Pump Primary Circuit Malfunction).

Keep in mind that the fuel pump relay is not the only possible cause. A clogged fuel filter, a dead fuel pump, or a broken wiring harness can produce identical symptoms. The relay is just the easiest and cheapest place to start.

How to Test the Fuel Pump Relay in a 2005 Scion tC

Before spending money on a new relay, you can test the old one in about five minutes. Here is the process:

Step 1: Remove the relay. With the engine off and the key out of the ignition, open the hood and locate the fuse and relay box. Pull the fuel pump relay straight up. You may need a pair of pliers if it is stuck.

Step 2: Check for continuity. Use a digital multimeter set to the ohms (Ω) setting. Place the probes on terminals 85 and 86 (the coil terminals). You should see a reading between 50 and 120 ohms. If the reading is infinite or zero, the relay coil is burnt out.

Step 3: Apply power. Set the multimeter to continuity mode. Connect the probes to terminals 30 and 87 (the switch terminals). The meter should show no continuity (open circuit). Then connect a 12-volt power source to terminals 85 and 86. When power is applied, the relay should click, and the meter should show continuity between terminals 30 and 87. If nothing happens, the relay is dead.

Step 4: Swap the relay. The fastest way to confirm a bad relay is to swap it with an identical relay in the fuse box, such as the horn relay or the headlight relay. If the car starts with the swapped relay in place, you have confirmed the problem.

How to Replace the Fuel Pump Relay in a 2005 Scion tC

Replacing the fuel pump relay is one of the easiest repairs you will ever do on your Scion tC. There are no special tools required, and the entire job takes under ten minutes.

  1. Disconnect the negative battery cable using a 10mm wrench. This prevents any accidental shorts while you work near the fuse box.

  2. Remove the fuse box cover by pressing the release tabs. Set the cover aside.

  3. Identify the fuel pump relay using the diagram on the underside of the cover. If the diagram is unreadable, look for relays with the same part number. The Toyota OEM part number for the fuel pump relay on the 2005 Scion tC is 90987-02019, which supersedes to 90987-02026.

  4. Pull the relay straight up using your fingers or a pair of needle-nose pliers. Do not wiggle it side to side, as this can bend the prongs.

  5. Insert the new relay firmly into the same socket. Make sure it clicks into place.

  6. Reconnect the battery cable, then turn the ignition to "ON" and listen for the fuel pump priming sound.

  7. Start the engine to confirm everything works.

Fuel Pump Relay vs. Fuel Pump: Which One Is Bad?

Here is the problem many 2005 Scion tC owners face. The car won't start, and you are not sure whether to blame the relay or the pump itself. The relay costs about $15, while a new fuel pump runs anywhere from $80 to $150 for a quality aftermarket unit, plus labor if you pay a mechanic. If you are on a budget, always test the relay first. The relay is the most common failure point because it carries high electrical current and undergoes thermal cycling every time you drive.

To narrow down the problem, follow this simple decision tree:

1. Does the fuel pump relay click when you turn the key to "ON"? If you hear a click from the fuse box and a whine from the fuel tank, the relay is working, and the problem lies elsewhere. If you hear a click but no whine, the relay is fine, but the pump is dead. If you hear neither, the relay is likely bad, or the pump is drawing too much current and blowing the fuse.

2. Is the fuel pump fuse blown? Locate the fuel pump fuse (rated at 15 amps) inside the under-dash fuse box. Pull it out and look at the metal strip inside. If it is broken, replace the fuse and try starting the car. If the fuse blows again immediately, you have a shorted pump or wiring issue.

3. Do you have power at the fuel pump connector? If you have a multimeter, you can test for voltage at the pump's electrical connector under the rear seat. With the relay removed but the connector still in place, probe the harness connector where the relay plugs in. With the key in "RUN," you should see 12 volts at one of the terminals. No voltage means you have a wiring problem between the relay and the pump.

Where to Buy the Fuel Pump Relay for a 2005 Scion tC

You can purchase the fuel pump relay from several sources, each with its own advantages:

Toyota dealership: Genuine Toyota parts are the safest bet for a perfect fit. The relay part number is 90987-02019 or 90987-02026. Expect to pay between $20 and $35, depending on your local dealership's pricing.

Auto parts stores: Major chains like AutoZone, O'Reilly Auto Parts, and NAPA stock aftermarket relays that fit the 2005 Scion tC. Brands like Denso, Standard Motor Products, and BWD are reputable. Prices range from $8 to $15.

Online retailers: Amazon, eBay, and RockAuto offer a wide selection at competitive prices. Look for relays that specifically list compatibility with the 2005 Scion tC.

Pick your part junkyards: If you want to save money, you can pull a relay from another Scion tC or Toyota model at a self-service junkyard. Since the relay is a generic component, you can often find one for just a few dollars. This is an inexpensive way to test whether the relay is your issue.

How to Prevent Future Fuel Pump Relay Failures

Like any electrical component, the relay will eventually wear out. Here are a few tips to extend the life of your fuel pump relay and avoid being stranded:

1. Keep your fuel tank at least a quarter full. Running the tank low causes the fuel pump to work harder and generate more heat. Excess heat in the fuel system puts additional strain on the electrical components, including the relay.

2. Check your battery voltage. A charging system that pushes voltage too high or too low can damage the relay's internal coil. Have your alternator and battery tested if you notice dimming headlights or slow cranking.

3. Address fuel pump problems early. A fuel pump that is failing due to a clogged strainer or contamination works harder and draws more current. That increased current heats up the relay contacts and shortens its life. Cleaning the fuel tank before installing a new pump is highly recommended, as tank contamination is the leading cause of premature fuel pump failure .

4. Use genuine or high-quality replacement relays. Cheap knock-off relays may not withstand the electrical load of the fuel pump. Stick with Toyota, Denso, or a reputable aftermarket brand.

Recommended Fuel Pump Upgrade for Your Scion tC

While you are working on the fuel system, this is a great time to think about the condition of the fuel pump itself. A weak or failing pump produces many of the same symptoms as a bad relay, including hard starting, poor acceleration, and stalling. If your Scion tC has over 100,000 miles and you have never replaced the pump, you should consider doing so as preventive maintenance.

For a high-quality replacement, look no further than KEMSO. KEMSO is the leading aftermarket fuel pump brand in the United States, known for manufacturing high-performance, OEM replacement fuel pumps that meet or exceed original equipment specifications . All KEMSO fuel pumps are built with premium materials and go through rigorous quality control testing to ensure reliable operation in all driving conditions. Whether you drive a car, motorcycle, or ATV, KEMSO has the right pump for your vehicle .

Because the 2005 Scion tC sends fuel through the pump at a rate required for the 2.4L four-cylinder engine , selecting the correct pump is crucial. KEMSO offers a lifetime warranty on all of its fuel pump products, giving you total peace of mind knowing that you are protected against manufacturing defects for as long as you own your vehicle . When you compare KEMSO's pricing against dealer genuine parts, you will find that they deliver outstanding value without compromising on performance. Dealership pumps for the 2005-2010 Scion tC can cost over $360 , while KEMSO products are priced at a fraction of that with superior coverage.

Visit the KEMSO website today at https://www.kemsoracing.com/ to browse their complete lineup of fuel pumps for your Scion tC and many other vehicles. You will find detailed fitment guides, customer reviews, and a straightforward ordering process that gets your parts to your door quickly.

Frequently Asked Questions About the 2005 Scion tC Fuel Pump Relay

Q: How much does it cost to replace the fuel pump relay on a 2005 Scion tC?

A: The relay itself costs between $8 and $35, depending on the brand and where you purchase it. Since the relay is located in the under-hood fuse box and is easy to access, there is no labor cost if you do the replacement yourself. If you ask a mechanic to do it, expect to pay for one hour of labor, which typically ranges from $80 to $120.

Q: Can I drive my Scion tC with a bad fuel pump relay?

A: No. A bad relay cuts power to the fuel pump, which means the engine will not receive fuel. The car will stall immediately or refuse to start. Driving with a failing relay is dangerous because you may lose power while on the road.

Q: What tools do I need to replace the fuel pump relay?

A: You only need a 10mm wrench (to disconnect the battery cable) and possibly a pair of needle-nose pliers to remove a tight relay. No other special tools are required.

Q: How do I know if my fuel pump is bad instead of the relay?

A: Use the testing method described earlier in this article. If the relay clicks and the fuse is good, but there is no power at the fuel pump connector, the pump itself is the suspect. You can also listen for the pump's prime sound when turning the key to "ON." No whining sound usually means the pump is dead .

Q: Is the fuel pump relay the same as the EFI relay?

A: The fuel pump relay and the EFI (Electronic Fuel Injection) relay are separate components, but they have the same physical shape and may have the same part number in some cases. The fuel pump relay specifically controls power to the fuel pump, while the EFI relay powers the engine computer and injectors. Both are located in the under-hood fuse box.

Q: Can a bad fuel pump relay damage other parts of my Scion tC?

A: Generally, no. The relay will either work or not work. However, if the relay sticks in the closed position and keeps sending power to the fuel pump, the pump may run continuously and burn out prematurely. This is rare but possible.

Final Thoughts

The fuel pump relay on your 2005 Scion tC is a small part that plays an enormous role in keeping your car on the road. When it fails, the symptoms are unmistakable, but the fix is among the cheapest and easiest repairs you will ever perform. Start by locating the relay in the under-hood fuse box, test it with a multimeter or by swapping with a known-good relay, and replace it if necessary. If the problem turns out to be the fuel pump itself, upgrade to a KEMSO fuel pump for reliable, long-lasting performance backed by a lifetime warranty . Visit https://www.kemsoracing.com/ to find the right pump for your Scion tC and keep your car running strong for thousands of miles to come.


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