2008 Pontiac G6 Fuel Pump Relay: Location, Testing, and Replacement Guide

The bottom line up front: The fuel pump relay on a 2008 Pontiac G6 is located in the luggage compartment fuse box, which is inside the trunk on the driver's side behind a removable cover. It is labeled as position #25 in the rear fuse block. If your G6 cranks but won't start, stalls unexpectedly, or the fuel pump runs continuously, the relay is one of the first components to check before spending money on a new pump. This relay controls the power supply to the in-tank fuel pump, and a failing unit can cause a range of frustrating driveability problems.

Understanding the 2008 Pontiac G6 Fuel Pump Relay

The fuel pump relay is an electromechanical switch that controls the power flow to the fuel pump. When you turn the ignition key to the ON position, the engine control module (ECM) activates the relay, which sends battery voltage to the in-tank fuel pump. The pump pressurizes the fuel system to deliver fuel to the injectors.

The ECM will disable the fuel pump relay within 2 seconds unless it detects ignition reference pulses from the crankshaft position sensor. This is a safety feature that prevents the pump from running if the engine is not actually cranking or running. The ECM continues to enable the relay as long as the engine is running and the ignition reference pulses are present. If the engine stalls or the ignition is turned on without cranking, the relay shuts off after about 2 seconds.

The 2008 G6 uses a returnless, on-demand fuel system design. The fuel pressure regulator is built into the fuel sender assembly inside the tank, which eliminates the need for a return fuel line from the engine. This design helps keep the fuel temperature lower inside the tank and reduces evaporative emissions.

Where Is the 2008 Pontiac G6 Fuel Pump Relay Located?

The 2008 Pontiac G6 has three fuse boxes, which can be confusing for DIY owners. Here is a breakdown:

  1. Passenger Compartment Fuse Box: Located on the passenger's side of the center console, near the floor. This box contains fuses for interior components like power windows, radio, and HVAC controls, but it does NOT contain the fuel pump relay.

  2. Engine Compartment Fuse Box: Located in the engine bay on the driver's side near the battery. This box contains fuses and relays for major engine and electrical systems, including the cooling fans, starter, and powertrain control module. However, the fuel pump relay is not located here on the Pontiac G6.

  3. Luggage Compartment Fuse Box (Rear Fuse Block): This is where you will find the fuel pump relay. To access it:

    • Open the trunk of your Pontiac G6.
    • Find the fuse panel on the driver's side of the rear cargo area.
    • Remove the plastic cover, which snaps off easily by hand. You may need to remove any carpet or cargo mat that covers the panel.
    • The relay is located at position #25 according to fuse box diagrams for the 2005-2010 Pontiac G6. Some diagrams also list a fuel pump fuse at position #37 and a fuel pump relay at position #25.

The fuel pump relay is a gray relay, part number 13503102, which is shared with several other GM vehicles. It is a standard automotive relay that can be found at most auto parts stores.

Symptoms of a Failing Fuel Pump Relay on a 2008 G6

A failing fuel pump relay can cause several noticeable symptoms:

1. Crank but No Start: This is the most common symptom. The engine cranks over, but it will not fire because the fuel pump is not receiving power. This can be intermittent, especially when the relay heats up.

2. Engine Stalls While Driving: If the relay fails while the engine is running, the fuel pump will lose power, and the engine will stall. The engine may restart after the relay cools down, which can be confusing.

3. Fuel Pump Runs Continuously: If the relay contacts weld together or short internally, the fuel pump may run continuously, even with the ignition off. This will drain the battery and can flood the engine.

4. No Fuel Pump Prime: When you turn the ignition to the ON position, you should hear the fuel pump prime for about 2 seconds. If you hear nothing, the relay or its control circuit may be faulty.

5. DTC P0230: The ECM may set diagnostic trouble code P0230 (Fuel Pump Relay Control Circuit) if there is an issue with the relay control circuit.

How to Test the Fuel Pump Relay on a 2008 Pontiac G6

Before you buy a new relay, it is wise to test the existing one. Here is a step-by-step process based on the factory diagnostic procedure:

Step 1: Listen and Feel for the Click. With the ignition in the OFF position, have a helper turn the key to the ON position without starting the engine. Place your hand on the relay in position #25 in the rear fuse block. You should hear and feel a single click as the relay activates. The fuel pump should also run for about 2 seconds and then stop. If you hear nothing, the relay or its control circuit may be faulty.

Step 2: Swap the Relay. The rear fuse box contains several relays of the same type. Look for relays that are the same color and have the same pin configuration. For example, the rear window defogger relay (position #26) or the park lamp relay (position #27) may be identical. Swap the suspected fuel pump relay with a known working relay. If the fuel pump now works, the original relay is bad.

Step 3: Bench Test the Relay.

  1. Remove the relay from the fuse block.
  2. Measure the resistance between terminals 85 and 86. You should read 70-110 ohms. If the resistance is out of spec, the relay coil is bad.
  3. Measure the resistance between the following terminals. You should have infinite resistance (no continuity) on all of these readings:
    • Terminals 30 and 86
    • Terminals 30 and 87
    • Terminals 30 and 85
    • Terminals 85 and 87
      If continuity is detected, the relay contacts are shorted.
  4. Connect a 20A fused jumper wire from the positive battery terminal to relay terminal 85. Connect another jumper wire from the negative battery terminal to relay terminal 86. The relay should click. Now measure resistance between terminals 30 and 87. You should read less than 2 ohms. If it measures more, the relay contacts are burned or worn.

Step 4: Test the Relay Socket with a Test Lamp.
With the relay removed and the ignition ON, probe the control circuit terminal 86 of the relay socket with a test lamp connected to a good ground. Command the fuel pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF with each command.

  • If the test lamp does not turn ON and OFF, test for an open or short to ground in the fuel pump relay control circuit, or check for an intermittent or poor connection at the ECM.
  • If the test lamp remains illuminated with each command, test for a short to voltage in the control circuit.

A Known Issue: Terminal Tension and the Hot Soak No-Start

There is a documented GM service bulletin (PI1462) that addresses a specific intermittent starting issue on the 2006-2010 Pontiac G6. The primary symptom is a "crank but no start" condition that typically occurs after the vehicle has been driven and then sits for a short period, often called a "hot soak".

According to the technical investigation, the root cause is reduced terminal tension in the body-side harness connector that interfaces with the rear fuse block. Specifically, the terminal at Rear X1 Pin A10, which belongs to the fuel pump relay circuit, develops increased electrical resistance. This resistance prevents the fuel pump from receiving the necessary B+ voltage to operate during the hot soak period.

Because the issue is related to terminal tension and heat-induced resistance, the electrical connection may temporarily improve as the components cool down, which is why the vehicle may start after a longer rest period. If you are experiencing this specific pattern of failure, you may need to address the harness terminal issue rather than just replacing the relay.

How to Replace the Fuel Pump Relay on a 2008 Pontiac G6

Replacing the fuel pump relay is a simple task that takes about five minutes:

  1. Disconnect the negative battery cable to be safe.
  2. Open the trunk and remove the cover from the rear fuse block on the driver's side.
  3. Locate the fuel pump relay at position #25.
  4. Use a relay puller tool or a firm grip to pull the relay straight out. If you do not have a relay puller, a pair of needle-nose pliers can work, but be careful not to damage the relay socket.
  5. Install the new relay, making sure it is fully seated in the socket.
  6. Reinstall the fuse block cover and reconnect the battery cable.
  7. Turn the ignition to the ON position and listen for the fuel pump to prime for about 2 seconds.

Choosing the Right Fuel Pump Relay

When you need a replacement fuel pump relay for your 2008 Pontiac G6, you have two main options:

1. Genuine GM Relay: The factory part number for the fuel pump relay is 13503102, which is a gray relay. This part replaces several older numbers, including 12193604, 15328864, 12088592, 12177236, 12088576, 12193614, and 12135175. It is covered by the GM factory warranty. You can also use the black relay, part number 13503103, which is listed as an interchangeable "Relay Assembly, Fan Control" for the G6, and it replaces even more part numbers.

2. Aftermarket Relay: A standard 30-amp automotive relay will work. Just make sure it has the same pin configuration (typically terminals 30, 85, 86, and 87). You can find these at most auto parts stores.

The relay is not expensive. The genuine GM gray relay (13503102) typically lists for around $16.90, and the black relay (13503103) lists for around $11.29. Aftermarket versions are usually even cheaper.

The 2008 G6 Fuel Pump Relay and Fuel Pressure

Once you confirm the relay is working, it is helpful to understand the fuel pressure specifications for your G6. According to the factory service information, the fuel pressure should be 345-414 kPa (50-60 psi) when the fuel pump is commanded ON. The fuel pressure should stabilize and remain constant once the pump stops, and it should not drop more than 34 kPa (5 psi) in one minute.

If the fuel pressure is too low, you may have a restricted fuel feed pipe, poor harness connections, or a faulty fuel sender assembly. If the pressure drops quickly after the pump stops, you may have a leaking fuel pressure regulator or a faulty check valve in the fuel pump assembly.

KEMSO Fuel Pump Recommendation

If your 2008 Pontiac G6 fuel pump itself is failing and you need a reliable replacement, consider a high-performance fuel pump from KEMSO. KEMSO fuel pumps are designed as OEM replacements, which means they are built to meet or exceed the specifications of the factory original part. Whether you drive a Pontiac G6 or another vehicle in your garage, KEMSO offers a range of fuel pumps for cars, motorcycles, and powersports vehicles.

KEMSO stands behind their products with a lifetime warranty, giving you peace of mind that your replacement pump is protected for as long as you own your vehicle. They are a trusted brand for DIY owners and professional mechanics who want dependable performance without paying dealership prices.

When you are ready to replace a failing fuel pump, visit KEMSO's website to see their full lineup of fuel pumps and find the right fit for your vehicle: https://www.kemsoracing.com/

Final Thoughts

The fuel pump relay on your 2008 Pontiac G6 is a small but critical component. Knowing its location in the rear fuse block, how to test it, and how to replace it can save you time and money. If you are facing a crank-but-no-start condition, always start with the simplest and cheapest parts first, and the relay is one of them. If the relay checks out, move on to checking the fuel pump fuse, the wiring, and the pump itself. And if you eventually need a new pump, KEMSO offers a reliable, warrantied replacement option that is worth considering.

For more information on KEMSO fuel pumps and other automotive parts, visit their website: https://www.kemsoracing.com/


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