2010 GMC Acadia Fuel Pump Relay Location - Find & Fix It Fast

If your 2010 GMC Acadia cranks but won't start, or experiences sudden engine stalls, the culprit could very well be a failed fuel pump relay. The vital fuel pump relay for your 2010 Acadia is located inside the engine compartment fuse box (also called the underhood fuse block or IPDM - Intelligent Power Distribution Module), specifically in position K46. This relay controls power to your SUV's fuel pump. Knowing exactly where to find it is the first critical step in diagnosing fuel delivery problems and getting back on the road.

Your fuel system relies on electrical control. The engine computer (PCM) commands the fuel pump relay to activate, which then sends battery power directly to the fuel pump itself. This happens every time you turn the key to the "Run" or "Start" position. If this relay fails, the signal is lost, and the fuel pump doesn't run, starving your engine of gasoline. No fuel means no start – simple as that.

While a completely dead relay is the primary suspect when facing a no-start condition where the engine cranks normally, issues like hard starting, intermittent stalling (especially when hot), or the engine dying suddenly without warning can also point towards a relay that's weakening or failing intermittently. Before condemning the fuel pump itself – a much larger and costlier repair – checking this relay is essential due diligence. It's a relatively inexpensive part and straightforward to access. A functioning relay is critical for reliable operation.

Pinpointing the Relay (Position K46)

The central hub for fuses and relays under the hood is your target. Here's the precise location step-by-step:

  1. Open the Hood: Securely prop the hood open.
  2. Locate the Fuse Box: Stand facing the front of your Acadia. Look near the top of the engine bay, positioned up against the firewall (the vertical metal partition separating the engine compartment from the passenger cabin). The fuse box you need is on the PASSENGER SIDE (right-hand side) of the firewall. It's a large, black, rectangular plastic box, usually held down with clips or screws.
  3. Open the Cover: The lid is secured with plastic clips. Feel around the edges and firmly press in or lift up on these clips to release them. Carefully lift off the cover once all clips are free. Set it aside safely.
  4. Identify Cover Legend & Internal Labeling: Flip the cover over. On its underside, you should find a detailed diagram (legend) showing the layout of all fuses and relays inside the box. Additionally, most 2010 Acadia fuse boxes have the circuit numbers (like F19, K46) or descriptive labels molded right onto the plastic inside the box itself, typically near each component slot.
  5. Find Position K46: Scan the diagram (either on the lid or inside the box) specifically for the relay positions labeled with a "K" followed by a number. You are looking for "K46". The diagram will show its exact grid location within the fuse box. Refer to any internal box labels to confirm visually.
  6. Visual Confirmation: Look at the cluster of square or rectangular relays within the fuse box. Find the specific slot labeled K46. The fuel pump relay itself is usually a standard automotive cube relay.

Understanding the Relay and Its Role

Relays are electromagnetic switches. They use a small electrical current from the Powertrain Control Module (PCM - your engine computer) to control a much larger current needed to operate a high-draw device like the fuel pump. This protects the delicate circuits in the PCM from the pump's amperage. The relay has internal contact points that physically close when energized, completing the high-current circuit to the pump. When the PCM removes the small control signal (like when turning the key off), an internal spring opens the contacts, stopping power flow to the pump. Reliability is paramount; failure disrupts this critical circuit.

Symptoms of a Failing Fuel Pump Relay

While the classic symptom is the engine cranking normally but refusing to start, be aware of other signs:

  • Engine Cranks But Won't Start: The most definitive sign. You hear the starter motor spinning the engine, but the engine never fires or runs. This strongly suggests a lack of fuel pressure.
  • Intermittent Starting Problems: The car starts fine sometimes, but other times it cranks endlessly without starting. This is a hallmark of a relay with failing internal contacts.
  • Engine Stalls Suddenly While Driving: A failing relay might abruptly cut power to the fuel pump mid-operation, causing the engine to die immediately. This can be dangerous, especially in traffic.
  • Engine Stalls When Hot ("Heat Soak"): Internal resistance in an aging relay can increase with heat, leading to failure precisely when the engine bay temperature is highest after running.
  • No Fuel Pump Prime Sound: When you first turn the key to "Run" (before cranking to start), listen near the rear seats/in the trunk. You should normally hear a distinct "humming" or "whirring" sound for about 2 seconds as the pump builds initial pressure. Complete silence here points strongly to a relay, fuse, pump wiring issue, or a completely failed pump.
  • Clicking Sound from Relay Area: Sometimes a failing relay might produce a rapid clicking noise near the fuse box when attempting to start, indicating it's receiving the signal from the PCM but failing to stay engaged and power the pump reliably. This symptom requires careful listening.

How to Test and Replace the Fuel Pump Relay in Your 2010 Acadia

WARNING: Always disconnect the negative battery terminal before working on any electrical components to prevent short circuits or shock.

Testing Method 1: The Swap Test (Simplest & Most Effective)

This is the most practical diagnostic method for most owners:

  1. Safety First: Turn the ignition OFF. Disconnect the negative (-) terminal from the battery using the appropriate wrench size. Secure the cable away from the terminal.
  2. Identify Known Good Relays: Open the underhood fuse box lid and locate the diagram. Find other relays in the box that are identical in physical size and terminal layout to K46. Common candidates include the horn relay (often K7, K10, or similar - check YOUR diagram!), HVAC fan relay, headlight relay, or starter relay (though the starter relay is usually different - stick to the horn or fan relay if possible). Choose a relay that powers a non-critical system you can test easily (like the horn).
  3. Carefully Remove K46 and the "Good" Relay: Squeeze or release any locking tabs, grip the relay firmly, and pull it straight up. Rocking gently side-to-side can help if it's stuck, but avoid using excessive force. Inspect the relay pins and the socket for corrosion.
  4. Swap the Relays: Place the suspect fuel pump relay (K46) into the socket where you took the known good relay from (e.g., the horn relay socket). Put the known good relay into the K46 socket.
  5. Reconnect Battery & Test: Reconnect the battery negative terminal. Attempt to start the engine. If the engine starts and runs now, your original K46 relay is bad.
  6. Check the Non-Critical System: Test the system controlled by the relay you used for swapping. If you used the horn relay socket, honk the horn. If the horn no longer works (but the car starts), it confirms the original K46 relay was faulty. Important: This step confirms the swap didn't just temporarily dislodge a bad connection elsewhere.
  7. Conclusion: If the car now starts properly with the known good relay in K46, and the horn (or other system) fails with the bad relay in its socket, you've confirmed the fuel pump relay (K46) is faulty and needs replacement.

Testing Method 2: Using a Multimeter (More Advanced)

  1. Prepare: Disconnect negative battery terminal. Remove relay K46.
  2. Identify Terminals: The relay base has multiple prong sockets (87, 30, 85, 86 - sometimes marked on case or diagram).
    • 87: Output to Fuel Pump (Pin removed: This socket connects internally to Pin 30 when relay clicks ON.)
    • 30: Battery Power Input (Constant 12V+)
    • 85: Coil Ground (Control Circuit - Path to Ground controlled by PCM)
    • 86: Coil Power (Control Circuit - Switched 12V+ from PCM during Start/Run)
  3. Test Coil Circuit:
    • Set multimeter to Resistance/Ohms (Ω).
    • Touch probes to pins 85 and 86 on the relay itself.
    • Read resistance: Should be between 50Ω-150Ω usually. Out of range = bad coil.
  4. Test Contact Circuit (Basic):
    • Set multimeter to Continuity (Beep) or Resistance/Ohms.
    • Touch probes to pins 30 and 87 on the relay itself. Meter should show NO continuity (infinite resistance or no beep) when relay is cool/off.
    • Apply direct 12V and Ground to pins 86 and 85 (use small wires/jumpers + battery).
    • When relay clicks: Meter should show continuity (very low resistance or continuous beep) between 30 and 87. Lack of continuity with power applied = bad contacts.
  5. Test Socket Power/Ground (Requires Ignition On):
    • Reconnect battery NEG. Leave relay OUT.
    • Set multimeter to DC Volts 20V range.
    • Probe Socket Pin 30: Connect red probe. Black probe to clean engine ground (e.g., bolt on body). Should show BATTERY VOLTAGE (~12.6V) with key OFF.
    • Probe Socket Pin 86: Connect red probe. Black probe to ground. Turn key to RUN (not start). Should show ~12V.
    • Probe Socket Pin 85: Connect red probe. Black probe to ground. Should show ~12V? If yes: Grounding issue. Confirm Ground: Set multimeter to Continuity/Ohms. Probe Pin 85 socket with relay out: One probe to Pin 85, other probe to known good ground (bolt). Key OFF. Should show very low resistance (near 0Ω). High resistance indicates a bad ground path back to the PCM/ECM.

Replacement Procedure:

  1. Confirm Failure: Ensure testing or symptoms strongly point to the relay.
  2. Obtain Correct Part:
    • Part Number: GM OEM part number is often 15307045, 15308857, 13580715, or similar (confirm for YOUR specific VIN/replacement year). A standard auto parts store relay matching the original's physical size, pin layout, and amperage rating (usually 20-30A contacts) will work.
    • Purchase: Buy from dealer, auto parts store (specify 2010 GMC Acadia - they will cross-ref), or reputable online retailer. Don't buy the cheapest generic relay; quality matters. Ask for a "standard Bosch-style automotive cube relay" (or bring the old one).
  3. Disconnect Battery: Always disconnect the negative terminal.
  4. Locate & Remove K46: Access the underhood fuse box, lift the cover, identify position K46, and remove the old relay by pulling it straight out. Note its orientation if it has an arrow or specific pin offset.
  5. Install New Relay: Orient the new relay correctly (match the pin layout - it usually only fits one way due to offset pins or notches). Press down firmly until it seats completely.
  6. Reconnect Battery: Secure the negative terminal.
  7. Test: Turn the ignition key to "Run" and listen for the fuel pump priming sound for 1-2 seconds. Attempt to start the engine. Verify normal operation.
  8. Replace Fuse Box Cover: Securely clip the fuse box lid back into place. Close the hood.

Crucial Check - The Fuel Pump Fuse

Even if the relay works, a blown fuse will still prevent power from reaching the pump.

  1. Location: Inside the same engine compartment fuse box.
  2. Finding the Fuse: Consult the diagram on the fuse box lid or inside labeling. Look specifically for "Fuel Pump", "FP", "Fuel Sys/Ign" or similar description. On the 2010 Acadia, the primary fuel pump fuse is often Fuse F19 (a 20 Amp fuse). However, ALWAYS confirm using YOUR fuse box diagram as locations can vary slightly depending on exact trim level or build date. It's typically a mini blade fuse.
  3. Visual Inspection: Pull the fuse straight out using the fuse puller tool often provided inside the fuse box. Examine the thin metal strip inside the clear plastic body. If the metal is broken or melted, the fuse is blown.
  4. Replacement: If blown, replace it ONLY with a fuse of the exact same amperage rating (20A). Never use a higher-rated fuse. Reinstall the fuse fully. Reconnect the battery and test if the car starts. A blown fuse usually indicates a short circuit (like a damaged fuel pump drawing too much current). Replacing the fuse might get the car running temporarily, but if the underlying cause isn't fixed, it will likely blow again, pointing to another fault such as a failing pump or wiring harness issue. Consult a professional if the fuse blows repeatedly.

Preventative Maintenance and Tips

While relays are generally reliable for many years, consider these tips:

  • Quality Parts: Use quality replacement relays (OEM or known reputable brands like Bosch, Denso, Standard Motor Products). Cheap relays may have internal contact issues.
  • Inspections: When checking other fluids, quickly inspect the underhood fuse box for signs of corrosion, water intrusion, or damaged wires. Look at the relay itself periodically.
  • Address Electrical Gremlins: If experiencing other electrical issues, get them diagnosed. These can sometimes point to broader problems within the fuse box or wiring harnesses over time.
  • Professional Diagnosis: If you've replaced the relay and fuse (if necessary) and the car still won't start, or starts intermittently, the problem likely lies elsewhere:
    • Faulty Fuel Pump: The pump itself may have failed.
    • Wiring Harness Issues: Broken, corroded, or shorted wires leading to the pump (under the vehicle) or in the relay control circuit.
    • Failed PCM Command Signal: The PCM might not be sending the signal to trigger the relay due to an internal fault, faulty sensor (like a crank sensor sending no signal), or security system lockout.
    • Poor Ground Connection: A bad ground for the pump or the relay's control circuit (pin 85). Consult wiring diagrams.
    • Inertia Fuel Shutoff Switch: Your Acadia has a switch designed to cut fuel pump power in a collision. Located in the passenger footwell (front kick panel or behind trim), it might be tripped accidentally by a severe bump. Find it (refer to manual) and reset it if necessary.
    • Ignition Switch Issues: A worn ignition switch may not send the signal to the PCM or may not supply power to the RUN/START circuits.
    • Fuel Pressure Sensor: While less common as a primary no-start cause on this model.
  • Keep a Spare: Consider keeping a spare fuel pump relay specific to your Acadia in your glove box or center console. It's cheap insurance against being stranded.

Conclusion

The fuel pump relay (K46) in your 2010 GMC Acadia is the gatekeeper to engine starting. Located definitively inside the underhood engine compartment fuse box on the passenger side firewall, its failure causes frustrating no-start or stalling issues. Confirming its condition is far simpler and cheaper than replacing the fuel pump itself. Using the simple relay swap test with a known-good relay (like the horn relay) is the most effective diagnostic method for the average owner. Always remember to check the fuel pump fuse (typically F19, 20A) located in the same fuse box. Knowing exactly where K46 is and how to test it empowers you to diagnose a common cause of starting failure quickly and accurately, saving time, money, and hassle getting your Acadia back in reliable running order.

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