2002 GMC Sierra Fuel Pump Relay: Complete Guide to Location, Testing, and Replacement
The bottom line: If your 2002 GMC Sierra cranks but won't start, the fuel pump relay is often the first thing to check. The fuel pump relay is located in the under-hood fuse and relay box, and it controls power to the fuel pump. When this relay fails, your engine gets no fuel, and it won't fire up. Replacing it is a simple, low-cost fix that you can do yourself in about 10 minutes.
Where Is the 2002 GMC Sierra Fuel Pump Relay Located?
The fuel pump relay on a 2002 GMC Sierra sits in the under-hood fuse block, also called the power distribution center. Open the hood and look for the black plastic box near the battery on the driver's side. Pop the cover off, and you'll see a diagram on the underside of the lid. The fuel pump relay is typically labeled as "F/PMP" or "FUEL PUMP." If the label is faded, you can find it by looking for a small, cube-shaped relay with four prongs. It's usually positioned near the 20-amp fuel pump fuse.
For the 2002 GMC Sierra 2500 with a 6.0L V8, the relay location is the same — it's in the same under-hood fuse box, right next to the fuel pump fuse.
How Does the Fuel Pump Relay Work?
The fuel pump relay is an electrical switch that controls power to the fuel pump. When you turn the key to the ON position, the powertrain control module (PCM) sends a signal to the relay, closing the circuit and sending power to the fuel pump for about two seconds. This is the "prime pulse" — you can hear the fuel pump hum briefly when you turn the key. Once the engine starts and runs, the PCM keeps the relay engaged to maintain fuel pressure.
On alternative fuel models (LPG/CNG), the system is slightly different. There's an additional AF (alternative fuels) fuel pump relay that the alternative fuels ECM controls. When the engine runs on CNG, the AF fuel pump relay is energized to turn off the gasoline fuel pump, while the lock-off relay stays powered by the PCM.
Common Symptoms of a Bad Fuel Pump Relay
If the fuel pump relay goes bad, the fuel pump is left without power, and the engine won't get fuel. Here are the most common signs to watch for:
1. Engine cranks but won't start. This is the most obvious symptom. You turn the key, the starter spins the engine, but it never fires up because there's no fuel reaching the injectors.
2. No fuel pump noise at key-on. When you turn the key to the ON position, you should hear a brief humming sound from the fuel tank area. If you hear nothing, the relay might be dead.
3. Intermittent stalling. A failing relay can cause the engine to die unexpectedly while driving, then restart after a few minutes once the relay cools down.
4. Check engine light comes on. On some models, a bad relay can trigger diagnostic trouble codes related to the fuel pump circuit.
How to Test the 2002 GMC Sierra Fuel Pump Relay
Before buying a new relay, you can test it in a few simple steps. The best part is that testing costs nothing but a few minutes of your time.
Step 1: Listen for the prime pulse. Turn the key to the ON position (don't start the engine). Listen near the fuel tank for a two-second humming sound. If you hear it, the relay and pump are likely working. If not, move to step 2.
Step 2: Check the fuse. The fuel pump fuse is a 20-amp fuse located right next to the relay in the under-hood fuse box. Pull it out and hold it up to the light. If the metal strip inside is broken, replace the fuse.
Step 3: Try the relay swap trick. This is the quickest way to test the relay. The fuel pump relay is the same part as the horn relay, the A/C relay, and several other relays in the same fuse box. Simply swap the fuel pump relay with the horn relay. Turn the key to the ON position and listen for the fuel pump. If you hear it now, the original relay was bad.
Step 4: Use a test light. If you have a 12-volt test light, you can check for power at the relay socket. With the relay removed, probe the terminal that corresponds to pin 30 (constant power). It should be hot at all times. Then have someone turn the key to the ON position while you probe the control terminal (pin 85 or 86). The test light should illuminate briefly during the two-second prime pulse.
What OEM Part Number Do You Need?
The OEM fuel pump relay for the 2002 GMC Sierra is a standard 12-volt, 4-pin ISO micro relay. If you want to buy the genuine GM part, here are the numbers you need:
- Original GM part number: 12193613
- Superseded GM service part: 19118886
- Newer GM multi-purpose relay: 13503102 or 13500126
The 19118886 relay fits a wide range of GMC Sierra models from 1999 through 2014, including the 1500, 2500, and 3500 series with various engine options. It replaces many older part numbers, including 12177235, 12135086, 12135005, 12193613, 12177233, and 84095360.
Common Causes of Fuel Pump Relay Failure
Fuel pump relays don't fail often, but when they do, it's usually for one of these reasons:
1. Age and heat. The relay is located in the engine bay, where it's exposed to high temperatures. Over time, the internal contacts can wear out or corrode.
2. Electrical overload. If the fuel pump draws too much current due to a failing pump motor or a short circuit, it can damage the relay contacts.
3. Vibration. The constant vibration from the engine can cause the relay's internal connections to break over many years of use.
4. Moisture. If the under-hood fuse box gets water inside, it can corrode the relay terminals and cause intermittent failure.
How to Replace the Fuel Pump Relay on a 2002 GMC Sierra
Replacing the fuel pump relay is one of the easiest repairs you can do on this truck. You don't need any special tools, and the whole job takes less than 10 minutes.
Step 1: Locate the under-hood fuse box. Open the hood and find the black plastic box on the driver's side, near the battery.
Step 2: Remove the fuse box cover. Press the tabs on the sides and lift the cover off. Look at the diagram on the underside to find the fuel pump relay location.
Step 3: Pull out the old relay. Grasp the relay firmly and pull it straight out. It may take a little wiggling, but it should come out without much force.
Step 4: Install the new relay. Push the new relay straight into the same socket. Make sure it seats fully. You should hear or feel a slight click when it's in place.
Step 5: Test the repair. Turn the key to the ON position and listen for the fuel pump prime pulse. If you hear it humming for two seconds, the repair is successful.
What If the Relay Isn't the Problem?
If you've replaced the relay and the fuel pump still doesn't work, the problem could be elsewhere. Here are the next things to check:
1. Check the fuel pump ground. On the 2000-2002 GMC Sierra, the fuel pump ground is at connector G403, a stud on the left frame body-mount bracket. A rusty ground connection can kill the pump intermittently.
2. Test the fuel pump connector. At the tank, the 4-pin Metri-Pack 150 connector (GM part 12160482) has four wires: Pin B (gray, pump power), Pin C (black, ground), Pin A (purple, gas gauge signal), and Pin D (orange/black, sender return). If you have 12 volts on Pin B and a clean ground on Pin C during the prime pulse but the pump doesn't spin, the pump itself is bad.
3. Check the PCM fuel pump control circuit. The PCM sends a 12-volt signal on circuit 465 (dark green with white stripe) to energize the relay. If you have power at the relay socket but the PCM isn't grounding the relay coil properly, the circuit may be open.
4. Inspect the wiring harness. Look for damaged, melted, or corroded wires between the relay and the fuel pump. The gray wire (circuit 120) carries power from the relay to the pump, and any break in that wire will stop the pump.
Where to Buy the 2002 GMC Sierra Fuel Pump Relay
You have several options for buying a replacement relay. An OEM GM relay (part number 19118886) costs around $37 to $38 at a dealership, though the MSRP is higher at about $116. Online parts retailers like GM Parts Giant sell it for less, typically around $7 to $10 for the relay itself. Aftermarket brands like ACDelco (part D1780C), Bosch, and Standard Motor Products (part RY-612) also make compatible relays.
Why You Should Consider a Complete Fuel Pump Upgrade
If you're already troubleshooting the fuel system, it's worth thinking about the bigger picture. The fuel pump relay is just one component in the fuel delivery system. If your truck has high mileage, the fuel pump itself may be getting old. Replacing just the relay is a good short-term fix, but if the pump is weak or failing, you'll be back under the hood soon.
For owners who want reliability and performance, upgrading to a high-quality aftermarket fuel pump is a smart move. A quality pump delivers consistent pressure and flow regardless of engine load, which means better starting, smoother idling, and more dependable performance.
Recommended: KEMSO Fuel Pump for Your 2002 GMC Sierra
When it's time to replace your fuel pump or any fuel system component, the KEMSO brand stands out as a top choice. KEMSO is recognized as the US #1 aftermarket fuel pump for cars, motorcycles, ATVs, and UTVs . Their fuel pumps are designed as high-performance, OEM replacement parts that meet or exceed factory specifications.
All KEMSO fuel pumps are backed by a lifetime warranty, giving you serious peace of mind. Each pump has a serialized body that guarantees the warranty coverage. KEMSO's support team is based in the USA and staffed by American technicians who can help you with any questions.
KEMSO fuel pumps are designed for both gasoline and E85 fuel, and they feature a bypass valve set at 125.8 psi — higher than many competing pumps. They can support up to 600 BHP in naturally aspirated, turbocharged, and supercharged applications.
For the best selection of fuel pumps designed specifically for your vehicle, visit KEMSO Racing today at https://www.kemsoracing.com/ to explore their complete lineup of OEM-replacement and performance fuel pumps backed by lifetime warranties and USA-based technical support.