GMC Terrain front side marker bulbs use 194 size while rear side marker bulbs use 3057 size. The replacement chart covers 2010 through 2018 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC Terrain uses the 194 bulb for the front side marker position across the 2010-2018 model years.
The 194 is a miniature wedge bulb of the T10 type, rated at 12V and 3.78W, and is standardized under ANSI specifications for use in the United States and Canada.
The T10 wedge base of the 194 bulb is a common low-wattage format, typically associated with small indicator and courtesy lighting applications.
The rear side marker position on the GMC Terrain uses the 3057 bulb for the 2010-2016 model years.
The 3057 is a dual-filament wedge bulb of the T25 type, rated at 12V with a high filament of 27W and a low filament of 7W, and is also standardized under ANSI specifications for the United States and Canada.
The dual-filament design of the 3057 allows it to serve two distinct brightness levels within a single housing, which is a characteristic relevant to positions that may combine marker and stop or turn functions.
The 194 and 3057 are not interchangeable. They differ in base type, wattage, filament count, and physical size, with the T25 body of the 3057 being notably larger than the T10 body of the 194.
The front and rear side marker positions on the GMC Terrain use different bulb types, meaning a single replacement bulb does not serve both positions.