2024 GMC Sierra 2500HD Bulb Size Chart & Replacement Guide

As an ASE-certified master technician, I see a lot of heavy-duty trucks roll through the bay. The 2024 GMC Sierra 2500HD is an absolute powerhouse, but when a light goes out, figuring out exactly what bulb you need can be a bit confusing. The 2024 model year brought a massive styling refresh to the Sierra lineup, meaning advanced LED lighting is now standard across most trims (like the SLT, AT4, Denali, and Denali Ultimate). However, base models (like the Pro trim) may still utilize some traditional halogen or incandescent bulbs in the rear and auxiliary housings.

Whether you are looking to replace a burnt-out bulb on your base trim or hoping to upgrade some of the remaining incandescent bulbs to LEDs, this guide has you covered.

Quick reference

Below is the comprehensive bulb size chart for the 2024 GMC Sierra 2500HD. Note that many premium trims feature sealed LED assemblies that do not have replaceable bulbs.

Note: If your Sierra 2500HD has factory LED headlights or taillights (standard on most trims above the Pro), the bulbs cannot be replaced individually. The entire housing must be replaced if a failure occurs.

LED vs halogen upgrade considerations

If you own a Pro trim or another configuration that still utilizes incandescent bulbs for the turn signals, reverse lights, or license plate lights, upgrading to LEDs is a fantastic way to match the modern look of the front headlights. However, modern HD trucks are highly computerized. Here is what you need to know:

• CANBUS Errors and Hyperflashing: The Sierra's Body Control Module (BCM) monitors voltage. Because LED bulbs draw significantly less power than incandescent bulbs, the truck may think the bulb is burnt out. For turn signals, this results in "hyperflashing" (rapid blinking). To prevent this, you must install LED bulbs with built-in CANBUS decoders, or splice inline load resistors into the wiring harness.
• Space Limitations: High-output aftermarket LED bulbs often have large cooling fans or heat sinks on the back. Always ensure there is enough clearance behind the taillight housing or reverse light socket before purchasing.
• Color Temperature: If you are upgrading your reverse lights or license plate lights, aim for a 6000K crisp white color to perfectly match the factory LED headlights and DRLs.

How to replace each bulb

Tackling bulb replacements on a heavy-duty truck can be intimidating due to its sheer size, but most auxiliary bulbs are straightforward.

Headlights, Fog Lights, and DRLs On the 2024 Sierra 2500HD, these are fully integrated LED units across all trims. If a low beam or DRL strip fails, you cannot simply swap a bulb. You must replace the entire headlight assembly. This is usually best left to a professional, as it requires removing the front grille, fascia trim, and recalibrating the headlight aim after installation.

Taillights (Brake, Turn, and Tail) If you have the standard incandescent taillights (Pro trim), replacing the 7443 bulbs is simple. Open the tailgate and locate the two T15 Torx screws on the inside lip of the taillight housing. Remove them, and pull the taillight assembly straight back toward you. Twist the bulb socket counterclockwise to remove it, swap the bulb, and reinstall.

Reverse Lights The reverse lights (921 bulbs on base models) are accessed the exact same way as the taillights. Once the housing is pulled away from the truck bed, locate the lowermost socket, twist it out, and replace the bulb. Upgrading this specific bulb to a high-lumen LED is highly recommended for better visibility in your backup camera.

License Plate Lights These are accessible from under the rear bumper. Reach up behind the license plate step pad, find the small socket, twist it counterclockwise, and pull the 194 bulb straight out.

Common lighting issues for this generation

While the 2024 refresh is still quite new, it shares architecture with the slightly older 2500HD models. A few things to watch out for include:

• Moisture in the Headlight: Large temperature swings can occasionally cause condensation inside the large sealed LED headlight housings. A tiny amount of fogging that burns off quickly is normal; heavy water pooling means the factory seal has failed and the unit should be replaced under warranty.
• Trailer Wiring Faults: If your rear brake lights or turn signals act erratically, the issue is often traced to corrosion or debris in the 7-pin/4-pin trailer connector rather than a burnt-out bulb. The truck's advanced trailering system is very sensitive to voltage irregularities.

Electrical issues on modern, computer-heavy trucks can escalate quickly if not diagnosed properly. If you are dealing with persistent hyperflashing, dash warnings, or need a sealed LED assembly replaced, don't risk damaging your truck's wiring harness. Find a trusted shop on Repairius.