2023 GMC Sierra 1500 — Bulb Sizes (Headlight, Tail, Fog)

As an ASE-certified master technician, I regularly see late-model trucks like the 2023 GMC Sierra 1500 roll into the shop for lighting upgrades, repairs, and diagnostics. The 2023 model year sits in the post-refresh generation, where GMC transitioned heavily toward factory LED lighting across most trims. However, depending on whether you drive a base Pro, an SLE, an off-road-ready AT4, or a fully loaded Denali, your bulb sizes and assembly types can vary significantly.

Below is the definitive bulb size guide for the 2023 GMC Sierra 1500 to help you find the exact replacement you need.

Quick reference

Note: Trims like the SLT, AT4, Denali, and Denali Ultimate utilize sealed, integrated LED assemblies for most exterior lighting. For these, individual bulbs cannot be replaced; the entire housing must be swapped if it fails. Lower trims (Pro, SLE) may still use replaceable halogen or incandescent bulbs in certain locations.

LED vs halogen upgrade considerations

If you own a lower trim 2023 Sierra 1500 with factory halogen bulbs, upgrading to aftermarket LEDs is incredibly popular, but it requires some technical know-how.

CANBUS Errors and Hyperflashing: The Sierra’s Body Control Module (BCM) monitors electrical resistance to detect blown bulbs. Because LEDs draw significantly less power than halogens, the BCM may think the bulb is dead. For turn signals, this results in "hyperflashing" (rapid blinking). To fix this, you will need LED bulbs with built-in CANBUS decoders, or you will need to splice inline load resistors into the wiring harness.

Headlight Dust Covers and Clearance: If you are upgrading base halogen H11 or 9005 bulbs to LED, be aware of the cooling fans on the back of the LED units. You must ensure there is enough clearance behind the bulb to reinstall the factory dust caps. If you leave the caps off, moisture will enter the housing and ruin the optics. Extended dust caps are available in the aftermarket if needed.

How to replace each bulb

• Headlights (Base Trims): Accessing the headlight bulbs requires reaching behind the headlight assembly. On the passenger side, you may need to remove the airbox for better clearance. Twist the dust cap counterclockwise, unplug the harness, and twist the bulb out.
• Fog Lights: These are accessed from under the front bumper or by pulling back the front wheel well liner. It’s a simple quarter-turn to remove the bulb.
• Tail Lights / Brake / Rear Turn: Drop the tailgate and locate the Torx screws on the inboard side of the tail light housing. Remove them, pull the housing straight back to release the alignment pins, and twist the bulb sockets out.
• License Plate Lights: These are easily accessible from under the rear bumper. Twist the socket out and pull the 194 bulb straight out of the wedge base.
• Interior Dome/Map Lights: Use a plastic trim removal tool to gently pry the plastic lenses off. Never use a metal flathead screwdriver, as the overhead console plastic scratches easily.

Common lighting issues for this generation

The 2023 Sierra 1500 is a robust truck, but it isn't immune to lighting quirks. The most common issue I see as a technician is moisture intrusion in the sealed LED tail lights on higher trims (especially the AT4 and Denali). If condensation builds up inside an integrated LED assembly, the internal boards can short out, requiring a complete (and often expensive) assembly replacement. If you notice this while under warranty, take it to the dealer immediately.

Additionally, owners who install low-quality aftermarket LEDs in their base-trim trucks often experience radio interference (static on FM/AM channels) due to unshielded LED drivers. Always opt for high-quality, shielded LED bulbs.

If you are dealing with complex electrical issues, a dead BCM channel, or you need an integrated LED assembly replaced and calibrated, don't guess—get professional help. Find a trusted shop on Repairius.