The fuel pump relay in a 2008 GMC Sierra is located in the engine bay inside the under-hood fuse/relay box (the Power Distribution Center). The relay is labeled FUEL PUMP on the diagram inside the lid.
For this model year and most GMT900 trucks (Silverado/Sierra from 2007 to 2013), the fuel pump relay sits in the engine compartment’s power distribution center on the driver’s side. There is also an interior fuse box, but the fuel pump relay itself is in the under-hood box. If you can’t spot it, remove the PDC lid and consult the diagram to identify the exact relay for your engine variant (4.8L, 5.3L, or 6.2L).
Locating the fuel pump relay in the engine bay
Use these steps to locate the fuel pump relay quickly. The following guidelines apply to this generation; your vehicle may have slight variations by engine and production year.
- Open the hood and find the large rectangular Power Distribution Center (PDC) in the engine bay, typically on the driver's side near the firewall or strut tower.
- Remove the PDC cover and read the diagram or labels inside to identify the relay marked FUEL PUMP or FUEL PUMP RELAY.
- If the label isn’t obvious, compare the relay positions to the fuse map printed on the cover or in the owner's manual to locate the correct relay for your engine.
- Note that while the exact label may vary (FUEL PUMP RELAY vs. FUEL PUMP), the position is consistent with the diagram for your engine configuration.
With the PDC opened and the diagram consulted, you should be able to identify the fuel pump relay quickly and proceed to testing or replacement if necessary.
Testing and troubleshooting the fuel pump relay
Before diving into tests, ensure you observe safety steps: the vehicle should be off and the engine cooled; for electrical tests beyond simple swapping, disconnecting the battery is advised. A practical diagnostic approach is to swap the suspected relay with a known-good relay from the same box and to verify fuel pressure if needed.
- Swap the suspected fuel pump relay with a known-good relay from the same relay block (for example, replace the fuel pump relay with a relay that you know works, such as the horn or A/C relay of the same type). If the vehicle starts or the pump runs after the swap, the original relay was likely faulty.
- With the ignition ON, check for voltage at the fuel pump connector or at the relay’s output terminal when the relay is energized. If there is no voltage, the problem may lie in the relay coil circuit or wiring rather than the pump itself.
- Check the related fuses feeding the fuel pump circuit to rule out a blown fuse before concluding the relay is bad.
- If you suspect the pump itself, perform a fuel-pressure test with a gauge to confirm adequate pressure once the pump is powered.
These steps reflect common diagnostics for this model; if any doubt remains, consult a service manual for your exact engine variant or a qualified technician.
Summary
In a 2008 GMC Sierra, the fuel pump relay is located in the engine bay’s Power Distribution Center and is labeled FUEL PUMP on the lid’s diagram. For quick troubleshooting, swapping the relay with a known-good one from the same box is a simple, non-destructive test, and verifying fuel pressure can confirm whether the issue lies with the relay or the pump itself.