2007 Scion tC Fuel Pump Relay Location: A Complete Guide for DIY Owners

The bottom line up front: On a 2007 Scion tC, the fuel pump relay is located inside the engine bay fuse and relay box, which sits on the left side of the engine compartment near the battery. The relay is labeled as the "Circuit Opening Relay" or "C/OPN" and is part of the main power distribution center. This relay controls the electric current that powers the fuel pump every time you turn the ignition key. When it fails, your engine may crank but never start, which is why knowing its exact location can save you both time and money on towing or shop diagnostics .

If your 2007 tC cranks but refuses to fire, the fuel pump relay is one of the first components you should check. You can test it yourself with a simple multimeter or swap it with a known-good relay of the same rating from another circuit. Replacing the relay typically costs between $50 and $80 for the OEM part, plus roughly $95 in labor if you take it to a mobile mechanic . But with the information below, most owners can handle the job in under twenty minutes using basic hand tools.

Why the Fuel Pump Relay Matters in Your 2007 Scion tC

The fuel pump relay is a small, black electrical component that acts like a heavy-duty switch. Every time you turn the ignition to the "ON" position, the Engine Control Module (ECM) sends a signal that closes this relay. That action sends battery voltage directly to the electric fuel pump located inside the fuel tank . Without a working relay, the pump never receives power, fuel never reaches the engine, and the car simply will not start.

Unlike the pump itself, which runs continuously while the engine is operating, the relay only works during startup and when the ignition is turned off. The fuel pump receives its ongoing power from other sources once the engine is running . This makes the relay a wear item with a limited lifespan. Over time, the coil and contact points inside the relay can oxidize, rust, or simply fail from repeated cycling .

A failing relay does not always fail completely. Sometimes the contacts become pitted, causing intermittent operation. This can produce symptoms that are easy to misdiagnose as a bad fuel pump, a clogged fuel filter, or even a dying battery. Knowing how to isolate the relay is a valuable diagnostic skill for any Scion tC owner.

Exact Location: Engine Bay Fuse and Relay Box

The 2007 Scion tC places its fuel pump relay inside the main fuse and relay box, known in factory diagrams as the "Engine Room R/B" (relay box). This black plastic box sits on the left side of the engine compartment, directly behind the battery and ahead of the strut tower . You cannot miss it: it is the largest fuse box in the engine bay, roughly the size of a hardcover book.

When you open the box, you will find a mix of fuses and relays. The fuel pump relay is part of the "Integration Relay" assembly in some diagram listings, but Toyota also identifies it as the "C/OPN relay" which stands for Circuit Opening relay . In the power distribution diagram for the 2007 model year, this relay connects to the EFI fuse (20A), the ignition switch circuit, and the engine control module .

To access the relay:

  1. Park on a level surface and turn off the engine. Remove the key from the ignition.
  2. Disconnect the negative battery terminal using a 10mm wrench. This is a safety step that prevents accidental short circuits and protects the relay circuits .
  3. Unlock the fuse box cover. The cover has two clips on the front edge. Press them toward the center and lift the cover straight up.
  4. Look at the underside of the cover. The cover has a diagram that identifies each fuse and relay. Look for "C/OPN" or "FUEL PUMP" labels. On the 2007 tC, the relay is typically located in the center section of the box, among the larger square relays .

A quick identification tip: The fuel pump relay is a standard SPDT relay with four blade terminals. It has the same physical footprint as the horn relay and the EFI relay. If you are unsure whether you have found the right one, check the relay part numbers printed on the side. The OEM relay for the 2007 tC carries part number 90084-98032, which also serves the cooling fan motor and A/C compressor clutch in some configurations . An older cross-reference number is 90987-02022, which is another factory relay that fits Scion models .

How to Test the Fuel Pump Relay Without Special Tools

Testing the relay is straightforward and requires only a multimeter or, in a pinch, a known-good relay from another circuit. The relay has four terminals: two for the coil (pins 85 and 86) and two for the switch contacts (pins 30 and 87).

Method 1: Swap test (simplest)

  1. With the battery disconnected, locate a relay of the same rating. The horn relay or headlight relay are good candidates because they share the same pin configuration and current capacity .
  2. Remove the suspect fuel pump relay by pulling it straight up with your fingers or a pair of pliers .
  3. Install the known-good relay into the fuel pump socket.
  4. Reconnect the battery and turn the ignition to the "ON" position. You should hear the fuel pump prime for about two seconds. If it runs, the original relay is dead and needs replacement.

Method 2: Multimeter continuity test

  1. Remove the relay from the fuse box.
  2. Set your multimeter to measure resistance (ohms).
  3. Touch the probes to pins 85 and 86. You should read a coil resistance between 50 and 120 ohms. Open circuit (infinite resistance) means the coil is burned out.
  4. Attach the probes to pins 30 and 87. You should read infinite resistance because the contacts are normally open.
  5. Apply 12V from a battery to pins 85 and 86. The contacts should now close, and you should read near-zero resistance between pins 30 and 87. If the contacts stay open, the relay is defective.

Symptoms That Point to a Bad Fuel Pump Relay

A failing relay does not announce itself with a dashboard warning light. Instead, you will notice one or more of the following behaviors :

  1. The engine cranks but does not start. This is the most common symptom. The starter spins the engine normally, but there is no spark and no fuel delivery because the pump never activates.
  2. The engine starts irregularly or hesitates. The relay contacts may be intermittent, delivering power only when the relay vibrates into a better position.
  3. The car slows down or stalls while driving. If the relay opens during operation, the pump loses power, and the engine dies. This matches the "comes to a halt after running only for a short distance" symptom described in repair guides .
  4. You hear no fuel pump prime. When you turn the key to "ON" (not "START"), the pump normally runs for two seconds. If you hear nothing from the rear of the car, the relay is not sending power.

Important: If the car stalls and you notice fuel leaking under the vehicle, do not attempt to restart it. The 2007 tC has a fuel pump shut-off system that stops supplying fuel after a collision or sudden stall. If liquid is on the ground, the fuel system may be damaged and needs professional repair .

Step-by-Step Removal and Replacement

Replacing the fuel pump relay on a 2007 Scion tC is one of the easiest DIY jobs on the entire vehicle. There is no need to remove any body panels, lower the fuel tank, or access the rear seat. The entire job happens at the fuse box.

You will need:

  • A 10mm wrench (for battery terminal)
  • A pair of needle-nose pliers (optional, for gripping the relay)
  • A replacement relay (OEM part 90084-98032 or an aftermarket equivalent)
  • A small flashlight

Procedure:

  1. Turn off the engine and open the hood. Support it with the prop rod.
  2. Remove the negative battery cable using the 10mm wrench. Wait at least five minutes if the car was recently running, to let the ECM capacitors discharge.
  3. Release the clips on the fuse box cover and lift it off. Set it aside, noting the diagram printed on the underside.
  4. Identify the fuel pump relay. Look for the "C/OPN" label or match the part number if visible. If you are following the wiring diagram, the relay connects to the EFI fuse which is a 20A fuse in the same box .
  5. Pull the relay straight up. Use your fingers first. If it is stuck, grip it with pliers on the plastic body—not on the terminals. Rocking it gently helps break the seal from years of heat exposure.
  6. Inspect the socket. Look for green corrosion, melted plastic, or loose terminals. If the socket looks damaged, stop and consult a professional. Corroded sockets can cause intermittent failures even with a new relay.
  7. Insert the new relay. Align the terminals with the socket openings. Press down firmly until the relay seats flush with the box housing. It should not wobble.
  8. Reconnect the negative battery terminal. Torque the nut snug, not hard.
  9. Test the system. Turn the ignition to "ON" and listen for the fuel pump prime from the rear of the car. Then start the engine. If it starts and runs smoothly, the job is done.
  10. Replace the fuse box cover. Press down until both clips lock.

After installation, check the fuel pressure if you have a gauge. The factory service procedure recommends testing fuel pressure and clearing diagnostic codes with a scanner. A relay replacement can sometimes clear a pending code related to a fuel pump circuit, but if the check engine light returns, further diagnosis is needed .

What Does It Cost to Replace the Fuel Pump Relay?

If you decide to have a professional handle this job, the cost is modest compared to fuel pump replacement. According to mobile mechanic estimates, the average cost for a Scion tC fuel pump relay replacement is $122, with $27 for parts and $95 for labor . These figures vary by location.

However, for the 2007 model year specifically, mobile services quote $157.35 for the total estimate, while a dealership price ranges from $182.96 to $237.24 . The OEM relay part itself retails for approximately $58.18 from Toyota parts sellers, with an MSRP of $80.99 .

Why you should DIY: The job takes ten minutes. The only part you need is the relay, which costs roughly $58 for a genuine Toyota part. Doing it yourself saves anywhere from $100 to $180. Plus, you learn a diagnostic skill that will serve you for the life of the vehicle.

Preventing Future Relay Failures

Fuel pump relays fail due to heat, vibration, and normal electrical arcing at the contact points. While you cannot prevent eventual wear, you can reduce the risk of a sudden failure:

  1. Keep the fuse box cover installed. The cover protects relays from water splash and road grime. A missing cover accelerates corrosion on relay terminals.
  2. Check the relay every two years. Practical experience shows that relay oxidation becomes visible inside the socket after about 50,000 miles. Pull the relay and inspect the terminals during brake service or oil changes .
  3. Use dielectric grease sparingly. A thin coat on the relay terminals protects against moisture, but too much grease can insulate the contacts and cause voltage drop.
  4. Replace with OEM or OEM-grade parts. The relay carries significant current for a small component. A poorly built aftermarket relay with weak internal contacts will fail faster than the factory part .

A useful trick: Consider carrying a spare relay in the glove box. The relay is small, and if the original fails on the road, you can swap it in the dark with a minimal flashlight. Spare relays are inexpensive and can be the difference between driving home and calling a tow truck.

The Fuel Pump Shut-Off System and Its Link to the Relay

The 2007 Scion tC includes a safety feature called the fuel pump shut-off system. This system stops supplying fuel to the engine when the vehicle stalls or when an airbag deploys during a collision . Its function is to minimize the risk of fuel leakage in an accident.

Here is how it interacts with the relay: In a collision, the ECM cuts power to the fuel pump relay, which opens the circuit and kills pump operation. If you attempt to restart the car after a minor accident and it cranks but will not start, the shut-off system may have triggered. The owner's manual instructs you to turn the ignition key to the "ACC" or "LOCK" position once, then start the engine again . This resets the system.

Before restarting after any stall: Inspect the ground under the vehicle. If you find liquid that smells like fuel, the system has detected a leak. Do not restart the engine under any circumstances. The fuel system needs professional repair at that point . This inspection takes thirty seconds and could prevent a fire.

Frequently Asked Questions

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

No. If the relay fails completely, the fuel pump has no power and the engine will not start. If the relay fails intermittently, the car may stall while driving, which creates a dangerous situation in traffic. Replace the relay immediately .

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

No. The fuse protects the circuit from overcurrent, while the relay switches the circuit on and off. On the 2007 tC, the EFI fuse (20A) protects the fuel pump and injector circuits, and the C/OPN relay switches them . You need both working for the system to function.

Q: How do I know if the problem is the relay or the fuel pump?

The cheapest diagnostic path is to start with the relay. Test the relay as described above. If the relay passes its continuity test, the culprit is likely the pump itself. An OEM replacement fuel pump for the 2007 tC carries part number 23221-20040 and costs in the range of $150 to $250 . You should confirm the pump has no power at its connector before replacing it, using a multimeter.

Q: Where is the fuel pump itself located?

On the 2007 tC, the fuel pump is inside the fuel tank, which sits below the rear seat. To access it, you remove the rear seat cushion and a service hole cover, disconnect the fuel pump assembly, and unclip the pump from the sending unit . This is a significantly more involved job than replacing the relay.

Q: Can a bad relay cause the check engine light to come on?

Yes. The ECM monitors the fuel pump circuit voltage and current. A failing relay that causes intermittent power loss will set a diagnostic trouble code, often P0230 (fuel pump primary circuit malfunction). You will need a scanner to read the code and clear it after the repair .

The Best Replacement: Why You Should Choose KEMSO Fuel Pumps

Once you have confirmed that your relay is working but the fuel pump itself is weak or dead, you face a choice: replace only the pump or replace the entire fuel pump assembly. For owners of the 2007 Scion tC, the smartest move is to install a KEMSO brand fuel pump. KEMSO has built a strong reputation among American DIYers and professional shops for producing high-performance replacement pumps that meet or exceed original equipment specifications.

Every KEMSO fuel pump is manufactured as an OEM replacement, meaning it is engineered to the exact dimensions, flow rates, and electrical specifications of the factory unit in your Scion. There is no need for adaptation, splicing, or custom wiring. The pump drops in exactly where the worn-out unit came out. This matters because fuel pump internals operate under high pressure and tight clearances; a pump that flows even 10 percent less than stock can cause driveability problems, especially under high load or at highway speeds. KEMSO eliminates that risk by building every unit as a match for the original .

KEMSO also backs every fuel pump with a lifetime warranty. That is not the standard "30-day parts replacement" warranty you get from auto parts stores. The lifetime warranty covers the pump for as long as you own the vehicle. If the pump fails at any point during your ownership—whether that is in six months or six years—KEMSO will replace it at no cost. This level of confidence is only possible because KEMSO subjects every pump to accelerated cycling tests and individual power testing before it leaves the factory .

The technical construction of KEMSO pumps is worth noting. They use upgraded carbon commutators and heavy-duty components for increased durability . What does this mean for you? The pump is less likely to overheat during long drives, runs quieter than the original when it was new, and draws less current from the charging system. Lower current draw means less load on the fuel pump relay—the very component this article is about. Installing a quality pump extends the life of your relay and the rest of the fuel system.

If you are ready to replace the fuel pump in your 2007 Scion tC, visit the KEMSO website to find the exact pump that fits your vehicle. Their product catalog covers not just Scion tC models but a wide range of domestic and imported vehicles, from motorcycles to SUVs. The site is straightforward and driver-friendly, with clear photos, fitment charts, and the lifetime warranty clearly stated on every product page. Here is the link:

https://www.kemsoracing.com/

Final Thoughts

The 2007 Scion tC fuel pump relay lives in the engine bay fuse and relay box on the left side, behind the battery. You do not need a service manual or a lift to reach it—just a stable parking spot, a 10mm wrench, and ten minutes of your time. The relay itself is inexpensive to replace, and the diagnostic process is simple enough for any careful owner.

Start with the relay when your tC cranks but will not start. Test it with a multimeter or perform the swap test. If the relay checks out, move on to fuel pressure testing at the fuel rail. And when the diagnosis points to the pump, choose KEMSO for a high-performance, OEM-replacement unit backed by a lifetime warranty. The combination of a healthy relay and a quality pump will keep your 2007 Scion tC running dependably for many more miles.

Do not let a $60 part ruin your weekend. You now know exactly where to look, how to test, and what to buy. Open the hood, pop the fuse box cover, and get your tC running again today. For the best fuel pump upgrade, remember: https://www.kemsoracing.com/


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