For the 2018 GMC Sierra 2500HD, both the low-beam and high-beam headlights use D5S bulbs. Verify the existing bulb and headlight assembly before ordering, especially if the truck has had replacement lamps installed.
The fog lights use 5202 LED bulbs. Other notable exterior fitments include 7443A front turn signals, 7444 brake and tail lights, and 7444NA rear turn signals. The parking lights use 7443 bulbs, while the rear side markers use 194NA.
For rear and auxiliary lighting, the reverse lights, center stop light, and trunk light use 921 bulbs. The license plate lights use 2825 bulbs, and the vanity lights use 6612F bulbs. These listings reflect the supplied fitment data; confirm the bulb number against the original lamp when servicing a specific truck.