2018 GMC Sierra 2500HD Bulb Size Guide

Quick reference

Note: Trim levels can affect the type of headlight bulb. The base models come with halogen H11 bulbs, while a 2018 GMC Sierra 2500HD Denali will have D5S HID bulbs. Always double-check your owner's manual or existing bulbs before purchasing replacements.

LED vs halogen upgrade considerations

When upgrading your 2018 GMC Sierra 2500HD to LED bulbs, there are a few things to keep in mind. While LEDs offer a brighter, more modern look and a longer lifespan, they can sometimes cause issues with your truck's electrical system.

• CANBUS Errors: The 2018 GMC Sierra 2500HD has a CANBUS system that monitors the lighting for any outages. Since LED bulbs draw less power than halogen bulbs, the system may think a bulb is burnt out and give you a "bulb out" warning on your dash. To fix this, you'll need to install a CANBUS-compatible LED bulb or an anti-flicker/resistor harness.
• Adapters: Some aftermarket LED bulbs may not fit directly into the stock housing. In these cases, you might need an adapter to secure the bulb. This is more common with headlight and fog light bulbs.

How to replace each bulb

• Headlights: To access the headlight bulbs on a 2018 GMC Sierra 2500HD, you'll need to remove the front grille and the headlight assembly. This can be a bit of a process, so be sure to have the right tools and a clean workspace.
• Fog Lights: The fog lights are located in the lower part of the front bumper and can be accessed from underneath the truck. You may need to remove a few screws or clips to get to the bulb.
• Turn Signals: The front turn signal bulbs are located in the headlight assembly, so you'll need to remove the assembly to access them. The rear turn signal bulbs are in the tail light assembly and can be accessed by removing the two screws on the inside of the tailgate.
• Brake and Tail Lights: The brake and tail lights are in the same location as the rear turn signals and can be accessed in the same way.
• Reverse Lights: The reverse lights are also located in the tail light assembly.
• License Plate Lights: The license plate lights are located above the license plate and can be accessed by removing the lens cover.
• Side Markers: The side markers are located in the front and rear of the truck and can be accessed by removing the lens cover.
• Dome/Map Lights: The dome and map lights are located in the overhead console and can be accessed by prying off the lens cover.

Common lighting issues for this generation

• Premature Burnout: Some owners have reported that their headlights and other bulbs burn out prematurely. This could be due to a number of factors, including a faulty voltage regulator or a poor connection.
• Condensation in Headlights: Another common issue is condensation building up inside the headlight assembly. This can be caused by a bad seal, which allows moisture to get in. If you notice condensation in your headlights, it's best to have them resealed or replaced as soon as possible to avoid any electrical issues.

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