2018 GMC Sierra 1500 bulb fitment starts with D5S bulbs for both the low-beam and high-beam headlights. The supplied fitment data does not identify a separate headlight configuration or projector/non-projector variation, so confirm the original bulb and housing before ordering.
- Front turn signals and parking lights use 7444NA bulbs.
- Rear turn signals use 7444NA, while the brake and tail lights use 7444.
- Reverse lights and the center stop light use 921 bulbs.
- License plate lights use 2825 bulbs.
- Rear side markers use 194NA bulbs.
- Interior vanity lights use 6612F; the supplied data also lists 921 for the trunk light.
No fog-light bulb fitment is listed in the supplied data. Match replacement bulbs to the listed function and verify the existing bulb if your Sierra has equipment-specific lighting.