2021 GMC Sierra 2500HD Fuse Box Diagram & Amperage

Quick answer

The 2021 GMC Sierra 2500HD has three main fuse box locations: under the hood (engine compartment), inside the cabin (driver's side dash kick panel), and in the rear (under the rear seat on the driver's side).

Having issues with your 2021 GMC Sierra 2500HD's electrical system? A blown fuse could be the culprit! This guide provides a comprehensive overview of the fuse box locations, diagrams, amperage ratings, and the circuits they protect. Remember to always consult your vehicle's owner's manual and the fuse box lid for the most accurate and up-to-date information, as fuse configurations can vary slightly due to trim levels and options.

Under-Hood Fuse Box

The under-hood fuse box is located in the engine compartment, typically on the driver's side near the battery. It contains fuses and relays for critical engine functions, powertrain control, major electrical systems, and trailer connections.

Relay Locations (Under-Hood):

• RL1 (Starter Relay): Controls power to the starter motor.
• RL2 (Fuel Pump Relay): Powers the fuel pump.
• RL3 (Ignition Relay): Supplies power to the ignition system.
• RL4 (Headlight Relay): Controls headlight operation.
• RL5 (Blower Motor Relay): Powers the blower motor for HVAC.
• RL6 (A/C Clutch Relay): Engages and disengages the A/C compressor clutch.
• RL7 (Trailer Brake Relay): Provides power for the trailer brake controller.

Cabin Fuse Box (Instrument Panel Fuse Block)

The cabin fuse box is located inside the vehicle on the driver's side, typically behind a removable panel on the side of the dashboard (the kick panel). This fuse box primarily handles interior electrical components, accessories, and convenience features.

Rear Fuse Box

The rear fuse box in the 2021 GMC Sierra 2500HD is typically located under the rear seat on the driver's side. This fuse box often contains fuses for electrical components found in the rear of the vehicle, such as trailer connections, power outlets, and certain body control functions.

How to Test a Fuse

If you suspect a blown fuse, here's how to safely test it:

1. Locate the Fuse Box: Refer to your owner's manual or the quick answer section above to find the correct fuse box.
2. Identify the Suspect Fuse: Open the fuse box lid and consult the diagram on the lid or in your owner's manual to find the fuse for the problematic component.
3. Carefully Remove the Fuse: Use a fuse puller (usually found within the fuse box or tool kit) to gently remove the suspect fuse. Never use metal tools that could short circuits.
4. Inspect the Fuse: Hold the fuse up to a light and look for a broken wire inside the fuse. If the wire is broken or charred, the fuse is blown. For blade-type fuses, you can also look for discoloration.
5. Use a Multimeter (Optional but Recommended): For a more definitive test, set your multimeter to the continuity setting. Touch one probe to each metal terminal of the fuse. A good fuse will show continuity (the multimeter will beep or display a reading close to zero ohms). A blown fuse will show no continuity.
6. Replace with a New Fuse: If the fuse is blown, replace it with a new fuse of the exact same amperage rating and type. Never use a fuse with a higher amperage, as this can lead to serious electrical damage or fire.

Common Blown Fuses on This Vehicle

While any overcurrent situation can blow a fuse, some fuses are more commonly affected due to their circuits or components. Here are a few to check first if you're experiencing related issues:

• Cigar Lighter / 12V Outlets: These fuses (often F3 in the cabin fuse box) are frequently blown due to short circuits from chargers, air fresheners, or other accessories. If your phone isn't charging, this is a good place to start.
• Blower Motor: If your HVAC fan isn't working on any speed, check the blower motor fuse (F5 in the under-hood fuse box or F1 in the cabin fuse box, depending on the fault). A failing blower motor or a blockage can draw excessive current.
• Headlights: If one or both of your headlights are out, check their respective fuses (F8 and F9 in the under-hood fuse box). While bulbs are a more common failure, a short in the wiring can blow the fuse.
• Trailer Brake Control: For those who frequently tow, the trailer brake control fuse (F4 in the under-hood or F15 in the cabin) can blow if there's a short in the trailer's wiring or the brake controller itself. Always inspect your trailer's wiring before troubleshooting the truck.

Always verify the printed legend in the fuse box lid against your owner's manual, as certain trim levels or optional equipment may have slight variations in fuse assignments.

Find a trusted shop on Repairius.