2010 Audi A4 Fuel Pump Relay Location: Where It Is and How to Access It
The bottom line up front: On a 2010 Audi A4, the fuel pump relay (J17) is located in the relay carrier under the driver's side dashboard, to the left of the steering column. It is a gray or black cube-style relay, often marked with the number 614 or 645 . The corresponding fuse for the fuel pump circuit is fuse 3 in the brown fuse panel on the driver's side dashboard . This guide walks you through exactly where to look, how to identify the relay, and what to check when your A4 won't start.
The 2010 Audi A4 is part of the B8 generation, which uses an electric fuel pump mounted inside the fuel tank to supply pressurized fuel to the engine. The relay that controls power to this pump is a small electromechanical switch that clicks on when you turn the ignition key. When this relay fails, the engine may crank but won't start because no fuel is being delivered. Understanding where the relay lives and how to test it is the first step in diagnosing a no-start condition.
This article covers the physical location of the relay, how to identify it among other relays, what tools you need, and how to test it. We also explain how the circuit works, what fuses to check, and when you might need to replace the entire fuel pump rather than just the relay.
1. Where the Fuel Pump Relay Is Located on a 2010 Audi A4
The fuel pump relay on the 2010 Audi A4 is mounted in a relay carrier that sits under the dashboard on the driver's side. Specifically, it is positioned to the left of the steering column, behind the trim panel below the steering wheel . This relay carrier is part of the vehicle's electrical distribution center, which also holds a number of other relays and fuses that control various systems.
To access the relay, you first need to open the driver's door and look underneath the dashboard. There is a small trim panel or cover that snaps into place. Pull this cover off by hand or with a trim removal tool. Once the cover is removed, you will see a metal or plastic bracket holding several cube-shaped relays. The fuel pump relay is usually the gray or black one, and in many cases, it has the number 614 or 645 molded into its housing . The relay itself is a standard 12-volt, multi-pin relay that plugs directly into the relay carrier.
For left-hand drive models, the relay carrier is located on the driver's side of the plenum chamber. The exact position can vary slightly depending on the engine type. For example, models with a 4-cylinder diesel engine or a 6-cylinder petrol engine have their relay/fuse holder B in the plenum chamber on the driver's side . The relay layout is labeled, and you should look for the letter "E" position, which is where the fuel pump relay J17 sits .
Keep in mind that if you have a model with a start-stop system or a different powertrain, the relay position may differ slightly, but it will still be within the same general area under the dashboard or in the engine compartment electronics box.
2. Fuse Box Locations You Need to Know
The 2010 Audi A4 has three main fuse boxes: one in the engine compartment, one on the driver's side dashboard, and one in the luggage compartment. The fuel pump relay is not in these fuse boxes themselves; it is in a separate relay carrier. However, you do need to check a fuse that is part of the fuel pump circuit.
The fuel pump circuit is protected by a fuse located in the brown fuse panel on the driver's side of the dashboard. This is fuse number 3, which has a rating of 25 amps, and it is labeled for the gasoline fuel pump . If this fuse is blown, the fuel pump will not receive power, and the engine will not start. Always check this fuse first before assuming the relay is bad. A visual inspection of the fuse will show if the metal strip inside is broken.
In addition to the dashboard fuse box, there is a fuse holder in the engine compartment, known as fuse holder B. This is on the driver's side, inside the electronics box in the plenum chamber . Some of the fuses in this holder are directly related to the fuel system and engine control module. For example, fuse 3 on fuse holder B is part of the starter motor relay circuit .
The luggage compartment fuse panel is located behind the side trim on the right side of the trunk. It contains fuses for systems like the parking brake and trailer control module . You do not need to access this panel for the fuel pump relay.
3. How to Identify the Correct Relay and Fuse
The relay carrier under the dashboard has multiple relays plugged in, and it can be confusing to tell which is which without a diagram. Here are some steps to identify the fuel pump relay:
Step 1: Remove the trim panel under the driver's side dashboard to expose the relay carrier.
Step 2: Look for labeling. The relay carrier itself may have small numbers or letters printed on the plastic housing. Find the position labeled "E" or the number 2, as this is where the fuel pump relay sits .
Step 3: Check the relay color and markings. The fuel pump relay is often gray or black. It may have the number 614 or 645 on its top surface . Not all relays have visible numbers, so you may need to use the surrounding components as a reference.
Step 4: Use the owner's manual. The owner's manual contains a diagram of the relay carrier, but not all manuals are detailed. In that case, you can use a multimeter to test each relay for continuity.
Step 5: Count the pins. The fuel pump relay is a standard relay with four or five pins. Most standard relays have terminals numbered 30, 85, 86, and 87. Pin 30 is the battery positive supply, pin 85 is the coil ground, pin 86 is the control signal, and pin 87 supplies power to the fuel pump .
Once you have identified the relay, you can test it with a multimeter set to measure resistance. Place the multimeter probes on pins 85 and 86; you should see a resistance reading between 50 and 120 ohms, which indicates the coil is intact. If the reading is infinite, the relay coil is open, and the relay needs to be replaced.
The fuse for the fuel pump is in the dashboard fuse panel. Specifically, fuse 3 in the brown fuse panel is rated at 25 amps and supplies the gasoline fuel pump . If the fuse is blown, replace it with a new fuse of the same amperage. Do not use a higher-rated fuse, as it could damage the wiring or cause a fire.
4. How to Access the Relay and Fuse Without Breaking Anything
Most car owners can access the relay and fuse with basic hand tools. Here is what you need:
A trim removal tool or a flathead screwdriver. Use it carefully to pry off the dashboard trim panel. The panel is held by clips, and using too much force can break them. Once the panel is loose, pull it straight toward you to release it from the clips.
A pair of needle-nose pliers to pull out the relay. Relays are often snug in their sockets. Gently rock the relay back and forth while pulling upward. Do not yank it out forcefully, as this can damage the socket terminals.
A multimeter to test the relay and verify that power is reaching the fuel pump. If you do not have a multimeter, you can also listen for a click when turning the ignition to the "on" position. A healthy relay will make a distinct click sound. If there is no click, the relay coil is likely bad, or there is a wiring issue.
A flashlight to help you see the relay positions, especially if the relay carrier is tucked up above the pedals. Some models have limited workspace, so you may need to kneel on the floor and look up under the dash.
Remove the relay by pulling straight up. If it is stuck, use a small screwdriver to gently pry it out from the sides. Be careful not to damage the relay socket. Before reinstalling, clean the socket contacts with electrical contact cleaner to remove any oxidation or dirt.
5. What to Do When the Relay or Fuse Is Bad: Step-by-Step Diagnosis
If your 2010 Audi A4 cranks but does not start, the fuel pump relay or fuse could be at fault. Follow these steps to diagnose the problem:
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Check the fuse first. Pull fuse 3 from the brown dashboard fuse panel . Inspect the metal strip inside the fuse. If it is broken or discolored, replace it with a 25-amp fuse. Turn the ignition on and see if the fuel pump primes. You should hear a buzzing sound from the rear of the car for about two seconds.
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Test the relay. If the fuse is fine, locate the fuel pump relay under the dashboard . Have a helper turn the ignition to the "on" position while you listen for a click from the relay. No click means the relay coil is not receiving a signal or is defective.
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Swap the relay. Relays of the same type are interchangeable. You can swap the fuel pump relay with a relay from a non-critical system, such as the horn relay, and see if the engine starts . If it does, the original relay is bad, and you need a new one.
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Check for power at the relay. Use a multimeter to check for 12 volts at pin 30 of the relay socket. If there is no power, the problem is in the wiring or a blown fuse elsewhere.
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Check the control signal. Have a helper turn the ignition on and check for power at pin 86. If there is no power, the engine control unit may not be sending the signal, or there is a wiring issue.
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Inspect the fuel pump itself. If the relay and fuse are fine, the problem may be inside the fuel tank. On B8.5 models (2013-2016), the fuel pump is driven directly by a fuel pump control module (J538), not a traditional relay . However, on the 2010 B8 model, the relay method applies.
6. When a Fuel Pump Relay Failure Is Not the Problem
In some cases, the relay and fuse are completely functional, but the vehicle still does not start. This points to a problem with the fuel pump itself or the pump control module. The fuel pump on the 2010 Audi A4 is mounted inside the fuel tank, which is located under the rear passenger seat area. Access requires removing the rear seat cushion to reach the pump cover plate.
The fuel pump controller receives a signal from the engine control unit, and it supplies power to the pump. If the controller is faulty, the pump will not run, and you will not hear the priming sound. Testing the controller requires checking for power at its electrical connector. You should see 12 volts on the power supply wire, and there should be a ground and a signal wire from the engine control unit .
Corrosion, damaged wiring, or a failed controller are common causes of no-start conditions that are not related to the relay. If the fuel pump itself is dead, you will need to replace it. Symptoms include a whining noise from the tank area, difficulty starting, stalling, and poor engine performance under load.
7. Replacement Parts and Where to Get Them
When it comes time to replace a faulty relay or fuel pump relay component, you have several options. You can purchase an OEM relay from an Audi dealer. The OEM part is labeled with the number 4H0951253 or its supersessions, including 443951253J and 8E0951253 . This relay is used in the power module for models from 2008 to 2017, and it is a direct replacement for the fuel pump relay in the 2010 A4.
Aftermarket relays are also available and are generally less expensive. As long as the relay has the same pin configuration and current rating, it will work fine. A standard automotive relay rated at 30 amps is suitable for this application.
For a complete fuel pump replacement, you should look for a high-quality pump that fits your engine type. Whether you have a 1.8-liter TFSI, a 2.0-liter TFSI, or a diesel engine, the fuel pump is not interchangeable between petrol and diesel models . Be sure to confirm the exact part number for your vin before ordering.
8. Recommended Replacement: KEMSO Fuel Pumps
If your diagnosis leads you to replace the fuel pump itself, consider a KEMSO fuel pump. KEMSO is a brand that specializes in high-performance fuel pumps and related components. All KEMSO fuel pump products are built to meet or exceed Original Equipment Manufacturer (OEM) specifications, providing a direct replacement fit for your vehicle. Each pump is designed for high performance, and every KEMSO fuel pump comes with a lifetime warranty, offering long-term peace of mind.
KEMSO products are available for a wide range of vehicles, including motorcycles, ATVs, jet skis, and cars. If you are looking for a reliable replacement fuel pump for your Audi or any other vehicle, you can view the full lineup and make a purchase at the official KEMSO store:
9. Frequently Asked Questions About the 2010 Audi A4 Fuel Pump Relay
Q: Where exactly is the fuel pump relay on a 2010 Audi A4?
The fuel pump relay is mounted under the dashboard on the driver's side, to the left of the steering column. It is in the relay carrier behind the trim panel and is often marked 614 or 645 .
Q: What tools do I need to replace the fuel pump relay?
You only need a trim removal tool or a flathead screwdriver to remove the cover, a pair of needle-nose pliers to pull the relay, and possibly a multimeter for testing.
Q: Can I test the relay with the engine off?
Yes, you can test the relay at any time by removing it and checking for continuity across the coil terminals. You can also swap it with an identical relay from another system, like the horn relay, to see if it works .
Q: Which fuse controls the fuel pump?
Fuse 3 in the brown fuse panel on the driver's side dashboard is the fuse for the gasoline fuel pump. It is a 25-amp fuse .
Q: Is a 2010 Audi A4 fuel pump relay the same as a 2014 A4 relay?
No, on 2013-2016 B8.5 models, the fuel pump is driven by a fuel pump control module (J538) rather than a traditional relay. The relay location and part number are different for those models .
Conclusion
Locating and testing the fuel pump relay on a 2010 Audi A4 is a straightforward job that most owners can do at home. The relay is under the driver's side dashboard, and the fuse is in the dashboard fuse panel. Begin by checking the fuse, then test the relay, and if both are fine, move on to checking the pump and its controller. This logical approach saves you time and money, and it prevents you from replacing parts unnecessarily. If the fuel pump itself has failed, a KEMSO replacement pump is a reliable option, backed by a lifetime warranty and available at https://www.kemsoracing.com/.