Audi A4 Fuel Pump Relay Location: Your Complete Guide (All Generations)

Finding the Audi A4 fuel pump relay location is critical if your car cranks but won't start. The exact location varies significantly depending on the model year (generation) of your A4, but we'll cover all possibilities from the B5 to B8/B8.5 models. The most common locations are either the driver's side footwell/kick panel relay panel or the main plenum chamber fuse/relay box under the hood.

If your Audi A4 cranks strongly but refuses to start, and you suspect a fuel delivery issue, the fuel pump relay is a prime suspect. This crucial electrical component controls power to the vehicle's fuel pump. When it fails, the pump doesn't activate, leaving your engine starved of fuel. Knowing precisely where to locate this relay across different A4 generations is the first step in diagnosing and resolving this common problem. This guide provides detailed, model-specific instructions to locate your fuel pump relay efficiently.

Understanding the Fuel Pump Relay's Role

Before diving into locations, grasp what the relay does. It acts as a heavy-duty electrical switch. A small current from the vehicle's ignition or Engine Control Module (ECM) triggers the relay. This allows a much larger current to flow from the battery through the relay directly to the fuel pump. This design protects sensitive control circuits from the high amperage needed by the pump motor. Symptoms of a failing relay include intermittent starting problems, a complete failure to start (with cranking), or a fuel pump that runs continuously if the relay contacts weld shut.

Safety First: Essential Precautions

Working on your vehicle's electrical system demands caution:

  1. Disconnect the Battery: Always disconnect the negative (-) battery terminal before inspecting or replacing fuses or relays. This prevents accidental short circuits that could cause sparks, damage components, or even start a fire.
  2. Use Correct Tools: Have appropriate trim removal tools (plastic pry tools) and screwdrivers (often Torx bits like T20 or T25) handy to avoid damaging panels or fasteners.
  3. Identify Correctly: Never remove or replace components blindly. Double-check relay and fuse identification charts specific to your year and model. Relying solely on physical position can be misleading.
  4. Mind Fuel Components: While primarily electrical, remember this system controls the fuel pump. Be mindful of fuel lines and fumes, though direct contact is usually not necessary for relay replacement.
  5. Consult Manuals: When in doubt, refer to your owner's manual or official Audi workshop information. Misdiagnosis can lead to unnecessary repairs or cost.

Locating the Audi A4 Fuel Pump Relay: Generation by Generation

1. Audi A4 B5 Generation (1996 - 2001): Under-Dash Convenience Control Module Panel

  • Primary Location: Look at the driver's side footwell (left-hand drive models) or passenger footwell (right-hand drive models). You need to access the Convenience Control Module Panel.
  • Access Steps:
    • Disconnect the negative battery terminal.
    • Remove the lower dashboard trim panel below the steering column (or glovebox area on RHD). This typically involves removing screws or plastic push-clips. Carefully pry the panel away starting from the edges.
    • Once the trim is removed, you will see a plastic box or panel mounted vertically. This is the Convenience Control Module Panel (CCM). It houses several relays and fuses.
    • Carefully unclip or unbolt the CCM cover to access the internal relays.
    • Specific Relay: On most B5 A4s, the fuel pump relay is usually Relay #167 (position numbers can vary slightly based on exact model year). Verify this by checking the diagram printed on the CCM cover itself or in your owner's manual. It will be one of the standard black cube relays.
  • Appearance: It will be a standard Bosch or Temic black plastic cube relay, typically with the number "167" marked on it or listed directly above its socket on the panel diagram.

2. Audi A4 B6 Generation (2001 - 2005): Driver's Footwell Relay Plate

  • Primary Location: The main relay panel shifts primarily to the driver's side footwell/kick panel area.
  • Access Steps:
    • Disconnect the negative battery terminal.
    • Locate the rectangular plastic trim panel on the side of the dashboard near the driver's left foot (LHD). This is the kick panel.
    • Remove the screws securing this panel (often Torx screws - T20 or T25 size). There might also be plastic push-pins near the bottom edge.
    • Carefully pull the panel down and away from the dashboard. It may still be tethered by wiring or clips, so avoid excessive force.
    • Behind this panel, you will find a large black relay carrier plate holding numerous relays and possibly some fuses.
  • Specific Relay: On B6 models, the fuel pump relay is consistently Relay #373. This is crucial and differs from earlier generations. Double-check the fuse/relay cover or the diagram printed directly onto the relay carrier plate. Relay #373 will be located among the other relays on this plate. It is also a standard black cube relay, similar to the B5, but marked or designated as 373.

3. Audi A4 B7 Generation (2005 - 2008): Dual Possible Locations

The B7 generation can have the relay in one of two locations, depending on the model year and engine type:

  • Option A: Driver's Footwell Relay Plate (Similar to B6):

    • Location: Driver's side footwell/kick panel (LHD models).
    • Access: Identical to the B6 (see steps above: disconnect battery, remove kick panel trim).
    • Specific Relay: Relay #373 remains the fuel pump relay for many B7 models. Always verify using the diagram on the relay plate cover or on the plate itself. If Relay #373 is present here, it's likely the fuel pump relay.

  • Option B: Plenum Chamber Main Fuse/Relay Box:

    • Location: Under the hood, in the plenum chamber area. This is the cavity beneath the windshield wipers and the black plastic cowl panel. This became increasingly common on later B7 models and is the standard location for the subsequent B8 generation.
    • Access Steps (Plenum Chamber):
      • Disconnect the negative battery terminal.
      • Carefully remove the plastic wiper arms. Lift the small cover at their base and loosen the nut (typically 13mm or similar). Gently rock the wiper arm off its splined shaft. Mark their position for reinstallation.
      • Remove the large black plastic cowl panel covering the plenum chamber. This involves releasing clips along its length (front and sides) and sometimes popping out plastic push-pins near the windshield edges. Work systematically from one end to the other using plastic trim tools.
      • Lift the rubber weatherstripping at the base of the windshield (it usually clips back easily).
      • Once the cowl panel is removed, you will see the large, usually dark gray or black, rectangular plenum chamber fuse/relay box (often called the "under-hood fuse box" or "relay carrier"). It typically has a main cover held by clips.
    • Specific Relay: Inside this plenum chamber box, the fuel pump relay is designated as Relay #373. It is one of several standard cube relays inside. Locate the relay/fuse diagram printed on the inside of the main cover – it will clearly show the position for Relay #373, labeled for the fuel pump. There may be secondary covers inside for fuses; you need access to the relay layer, which is usually underneath any fuse layers.

4. Audi A4 B8 / B8.5 Generation (2009 - 2016): Plenum Chamber Main Fuse/Relay Box

For the B8 generation (Sedan/Avant) and the facelifted B8.5, the location standardizes:

  • Primary Location: The plenum chamber main fuse/relay box under the hood.
  • Access: Identical to accessing the plenum chamber box on the B7 models (Disconnect battery, remove wipers, remove cowl panel).
  • Specific Relay: Relay #373 is confirmed as the fuel pump relay within the plenum chamber box. Crucially, always verify using the diagram printed inside the main cover of the plenum chamber fuse/relay box. Find the slot labeled "373" (or sometimes "J17" - a common internal designation for the fuel pump relay circuit).

Important Note for All Generations: Relay #373 and the J17 Designation

  • Across the B6, B7 (often), and B8 generations, Relay #373 is consistently used for the fuel pump circuit.
  • Internally, Audi often refers to the fuel pump relay as J17. This might be printed on the relay itself (or stamped into its plastic housing) or visible on wiring schematics. If you see "J17" on the diagram in your fuse box or relay panel cover, it corresponds to Relay #373 and the fuel pump function. Never rely solely on the physical appearance or position – the cover diagram is your authoritative source.

How to Replace the Audi A4 Fuel Pump Relay

Once you've located the correct relay:

  1. Safety: Ensure the negative battery cable is disconnected.
  2. Identification: Double-check you have the correct relay (#167 for B5, #373 for B6/B7/B8) using the diagram. Note its orientation in the socket.
  3. Removal: Grip the relay firmly and pull it straight out of its socket. It might be snug, but avoid excessive wiggling. Do not pry with screwdrivers directly on the socket.
  4. Inspection: Visually inspect the old relay for signs of overheating (melting, scorch marks). Also, check the relay socket pins for any damage, corrosion, or bent contacts. Clean contacts gently with electrical contact cleaner if corroded.
  5. Replacement: Take the new relay (ensure it's the correct Bosch or Audi part number). Orient it to match the old relay and the socket (look for pins of different widths or markings on the relay housing). Press it firmly and squarely into the socket until it seats completely and clicks. Do not force it.
  6. Reassembly: Reinstall any inner covers on the fuse box or relay panel. Securely replace the main cover.
  7. Reinstall Trim: Put the driver's kick panel trim or the plenum chamber cowl panel/wipers back in place securely. Ensure all clips are engaged and screws tightened appropriately.
  8. Reconnect Battery: Reattach the negative battery terminal.
  9. Test: Turn the ignition key to the "ON" position (don't start). You should hear the fuel pump whirring for a few seconds as it pressurizes the system. If you hear this sound return after silence, it's a good sign. Attempt to start the engine.

If the Problem Persists

If replacing the relay doesn't fix the no-start condition, consider:

  1. Fuse Check: Inspect the main fuel pump fuse, usually located in the same general area as the relay (driver's fuse panel, under-dash panel, or plenum chamber box). Refer to the specific fuse diagram for location and rating.
  2. Fuel Pump Health: The pump itself may have failed. Testing requires measuring voltage at the pump connector (during the priming cycle) and potentially listening for pump operation near the fuel tank.
  3. Ignition Switch/ECM: Faults in the ignition switch or Engine Control Module could prevent the signal reaching the relay.
  4. Wiring Faults: Breaks or shorts in the wiring harness between the relay and fuel pump, or between the ignition/ECM and the relay, could be the cause.
  5. Fuel System Issues: While the relay is common, problems like a clogged fuel filter, faulty fuel pressure regulator, or severely restricted fuel lines could also mimic symptoms.
  6. Professional Diagnosis: Due to the complexities of modern vehicle electronics and safety implications around fuel systems, seeking help from a qualified Audi technician or mechanic is advisable if the issue isn't resolved after checking the relay and fuses. They have specialized tools for diagnostics.

Conclusion: Pinpointing the Fuel Pump Relay Location is Key

Knowing the exact Audi A4 fuel pump relay location saves significant time and frustration during diagnosis. Always prioritize safety by disconnecting the battery. Remember the key locations: Convenience Module Panel for B5, Driver's Footwell Relay Plate for B6 (Relay #373), Driver's Footwell Relay Plate or Plenum Chamber Box for B7 (Relay #373), and definitively the Plenum Chamber Box for B8/B8.5 (Relay #373). Your most reliable tools are the fuse/relay panel cover diagrams specific to your vehicle's model year. While relay replacement is often straightforward, persistent issues warrant deeper investigation or professional assistance.

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