2003 GMC Sierra Fuel Pump Fuse: Complete Guide to Location, Diagnosis, and Replacement
The bottom line: The fuel pump on a 2003 GMC Sierra does not have a single fuse labeled specifically "fuel pump." Instead, the fuel pump is controlled through a relay in the under-hood fuse box, and that relay is protected by a fuse. If your truck won't start and you suspect a fuel delivery issue, the first thing to check is the fuel pump relay and the associated fuse in the engine compartment fuse box on the driver's side near the battery. The fuel pump fuse itself is typically a 20-amp or 10-amp fuse, and the relay is clearly marked in the fuse box diagram .
Where Is the Fuel Pump Fuse and Relay Located?
The 2003 GMC Sierra has two main fuse boxes. One is inside the cabin, and the other is under the hood. The fuel pump components are located in the under-hood fuse box .
Under-Hood Fuse Box Location: Open the hood and look on the driver's side, near the battery. The fuse block is a black plastic box with a removable cover. Lift the cover to access the fuses and relays .
Fuel Pump Relay: On the 2003 Sierra, the fuel pump relay is located in this under-hood fuse box. According to the official GM service manual and multiple fuse box diagrams, the relay is marked as "F/PMP" (Fuel Pump) or numbered as relay 29 in some diagrams . It is a standard relay that you can swap with another relay of the same type (like the horn or A/C relay) to test if it's faulty .
Fuel Pump Fuse: The fuse that protects the fuel pump circuit is also in the under-hood fuse box. On the 2003 GMC Sierra 2500 and 3500 models, the fuse is often a 10-amp or 20-amp fuse, depending on the engine and trim level. For example, the 2003 Sierra 3500 shows a fuse labeled "PCM. Fuel Pump" as a 20-amp fuse . For the 1500 and 2500 models, the fuse is often found in the engine compartment fuse box and is related to the PCM (Powertrain Control Module) power feed .
Passenger Compartment Fuse Box: There is also a fuse block on the driver's side edge of the instrument panel. However, the fuel pump relay and its primary fuse are not located here. The interior fuse box handles cabin electrical items like the radio, door locks, and power windows .
How to Test the Fuel Pump Relay and Fuse
If your 2003 Sierra cranks but won't start, the fuel pump may not be receiving power. Here is a simple step-by-step way to test the system.
Step 1: Listen for the Fuel Pump Prime. Turn the ignition key to the "ON" position (do not start the engine). You should hear a brief whirring sound coming from the fuel tank area, which is located under the rear of the truck. This sound lasts about 2 seconds as the fuel pump pressurizes the system. If you hear nothing, the pump is not getting power .
Step 2: Check the Fuel Pump Relay. Locate the fuel pump relay in the under-hood fuse box. Remove the relay. Look for a relay labeled "F/PMP" or "FUEL PUMP" on the fuse box cover diagram. If you are unsure, consult the owner's manual or fuse box diagram printed on the cover .
Step 3: Swap the Relay. Find another relay in the same fuse box that is the same part number and size. Common relays you can swap with include the horn relay or the A/C compressor relay. Swap the suspected fuel pump relay with the known-good relay. If the truck starts after the swap, the original relay was faulty .
Step 4: Inspect the Fuel Pump Fuse. Remove the fuse associated with the fuel pump. On the 2003 Sierra, this is often a 10-amp or 20-amp fuse. Look through the translucent plastic body of the fuse. If the metal strip inside is broken or melted, the fuse is blown. Replace it with a fuse of the exact same amperage rating .
Step 5: Use a Test Light. If you have a test light or a multimeter, you can probe the fuse terminals. With the ignition on, there should be power on both sides of the fuse. If there is power on one side but not the other, the fuse is blown. If there is no power at all, the issue may be further upstream, such as a bad ignition switch or a wiring problem .
What Causes the Fuel Pump Fuse to Blow?
A blown fuel pump fuse is usually a symptom of a deeper problem. Simply replacing the fuse without finding the root cause will likely lead to the fuse blowing again.
Faulty Fuel Pump. The most common cause is a failing fuel pump. As the pump wears out, its internal motor can draw excessive current or short out internally, which blows the fuse. This is a classic sign that the fuel pump needs replacement .
Short Circuit in the Wiring. The wiring harness that runs from the under-hood fuse box to the fuel pump can become damaged. This is especially common on older trucks where the wiring rubs against the frame or becomes corroded. A short to ground in this wiring will cause the fuse to blow immediately .
Corroded Electrical Connectors. The electrical connector at the top of the fuel pump module (inside the fuel tank) is exposed to fuel and moisture. Over time, the terminals can corrode, creating resistance and heat. This can cause the fuse to blow or the pump to stop working intermittently.
Intermittent Problems. Sometimes a fuse blows only after the truck has been driven for a while. This suggests an intermittent short or a pump that is failing when it gets hot. These are the hardest problems to diagnose because the fuse may appear fine when the truck is cold .
How to Replace the Fuel Pump on a 2003 GMC Sierra
If you have confirmed that the fuel pump relay and fuse are good, and the pump is still not running, the pump itself likely needs to be replaced. The fuel pump is located inside the fuel tank. Here is an overview of the process.
Step 1: Relieve Fuel System Pressure. Locate the Schrader valve on the fuel rail (the metal pipe running along the top of the engine). Place a rag over the valve and depress the valve core with a small screwdriver. Fuel will spray out. This step is critical for safety .
Step 2: Disconnect the Battery. Remove the negative battery cable to prevent any electrical sparks during the repair .
Step 3: Drain the Fuel Tank. If the tank is full, you will need to drain it. A full tank is very heavy and dangerous to lower. Use a siphon pump to remove as much fuel as possible into approved containers .
Step 4: Remove the Fuel Tank. Raise the truck securely on jack stands. Place a floor jack under the tank for support. Remove the tank straps and carefully lower the tank. Disconnect the fuel lines and electrical connectors as you lower the tank .
Step 5: Remove the Fuel Pump Module. Once the tank is on the ground, you will see a large locking ring on top of the tank. Use a hammer and punch or a special tool to rotate the locking ring counterclockwise. Lift the pump module straight out of the tank. Be careful not to damage the float arm or the strainer .
Step 6: Install the New Pump. Transfer any necessary components from the old pump, such as the rubber gasket, to the new pump assembly. Insert the new pump module into the tank, making sure it is properly aligned. Install the locking ring and tighten it securely.
Step 7: Reinstall the Tank and Test. Lift the tank back into position, reconnect all fuel lines and electrical connectors, and install the tank straps. Reconnect the battery. Turn the ignition to the "ON" position to prime the pump. Check for any fuel leaks before starting the engine .
Recommended Fuel Pump: KEMSO Fuel Pump
When it comes time to replace the fuel pump on your 2003 GMC Sierra, you want a part that is reliable, performs like the original, and is backed by a solid warranty. That is why we recommend the KEMSO Fuel Pump.
KEMSO fuel pumps are designed as high-performance, OEM replacement parts. They are built to meet or exceed the original equipment specifications, ensuring a direct fit and proper fuel pressure for your Sierra. Each KEMSO pump comes with a lifetime warranty, giving you peace of mind that your investment is protected.
If you need a new fuel pump for your 2003 GMC Sierra, visit the KEMSO website to find the exact pump for your truck. You can browse their selection of high-quality fuel pumps at:
Common Questions About the 2003 GMC Sierra Fuel Pump Fuse
Q: Does the 2003 GMC Sierra have a fuel pump shut-off switch?
A: No, the 2003 Sierra does not have a separate inertia switch like some Ford vehicles. The fuel pump is controlled entirely by the PCM (Powertrain Control Module) and the fuel pump relay. If the PCM does not see the engine cranking (ignition reference pulses), it will turn off the fuel pump relay after about 2 seconds .
Q: Why does my fuel pump run continuously?
A: If the fuel pump runs all the time, even with the key off, the fuel pump relay is likely stuck in the closed position. This is a common failure mode for relays. In this case, the relay has welded its contacts together, providing constant power to the pump. The solution is to replace the relay .
Q: Can I bypass the fuel pump relay?
A: Yes, you can temporarily bypass the relay for testing purposes. The under-hood fuse box has a fuel pump prime terminal that can be used to apply power directly to the pump. However, this is only for diagnostic purposes and should not be used as a permanent solution .
Q: What is the fuel pressure supposed to be on a 2003 GMC Sierra?
A: For gasoline engines, the fuel pressure should typically be between 55 and 62 PSI (pounds per square inch) at the fuel rail. If the pressure is significantly lower, the pump may be failing, or the fuel filter may be clogged .
Q: Is it safe to drive with a bad fuel pump relay?
A: No. If the fuel pump relay is failing, the truck may stall while driving and refuse to restart. This is a dangerous situation, especially on the highway. Replace the relay or the pump as soon as possible.
Final Thoughts
The 2003 GMC Sierra fuel pump fuse and relay system is straightforward once you know where to look. The key components are all in the under-hood fuse box on the driver's side. If you are experiencing a no-start condition, start with the simple checks: listen for the pump, swap the relay, and inspect the fuse. If those steps do not solve the problem, the fuel pump itself is likely the culprit.
When you need a replacement, choose a quality part that will last. A failing fuel pump is not something you want to replace twice. For a reliable, high-performance pump that comes with a lifetime warranty, check out the KEMSO Fuel Pump at https://www.kemsoracing.com/.