The GMC Terrain tail light requires bulb size 7440 or 3057 depending on the specific configuration of the vehicle. Available data covers the range from 2016 through 2020.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC Terrain inner tail light uses the 194 bulb across the 2010-2018 model years.
The 194 is a T10 miniature wedge bulb rated at 12V and 3.78W under the ANSI standard applicable in the US and Canada.
The GMC Terrain outer tail light uses the 3057 bulb for the 2010-2018 model years, while the 2019-2020 model years use the 7440 bulb instead.
The 3057 is a T25 dual-filament wedge bulb rated at 12V with a high filament of 27W and a low filament of 7W, conforming to the ANSI standard for the US and Canada.
The 7440 is a T20 single-filament wedge bulb rated at 12V and 21W under the same ANSI standard.
The outer tail light position on the 2019 GMC Terrain requires the 7440, which is a single-filament bulb, whereas the 3057 used in prior years carries a dual-filament design. These two bulbs are not interchangeable.
The wattage difference between the 3057 and the 7440 is notable: the 3057 high filament draws 27W while the 7440 single filament draws 21W, reflecting a functional difference in circuit design between the two generations.
All three bulb types specified for the GMC Terrain tail lights are wedge-base designs, meaning they are retained by socket friction rather than a bayonet or screw base.
The 194 bulb used in the inner tail light position operates at a significantly lower wattage (3.78W) than either outer tail light bulb, indicating a different functional role within the tail light assembly.