The GMC Terrain back up light utilizes a 921 bulb size for the specific lighting component located at the rear of the vehicle. Available data covers the period from 2010 through 2020 for the specified automotive application.
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 921 bulb for its back up light across the 2010-2020 model years.
The 921 is an ANSI-standardized bulb type, meaning its specifications are governed by a recognized industry standard applicable in both the United States and Canada.
The 921 bulb uses a wedge-style base, designated T15, which refers to a tubular bulb body approximately 15/8 of an inch wide that is held in its socket by friction rather than by pins or a bayonet mechanism.
The 921 operates at 12 volts and 16 watts, which are typical values for automotive reverse lighting applications.
The 2017-2020 GMC Terrain also specifies the 921 bulb for an inner back up light position, a separate fitment from the standard back up light.
Because both the standard back up light and the inner back up light on the 2017-2020 Terrain share the same 921 bulb size, the same replacement bulb serves both positions on those model years.
The wedge base of the T15 921 bulb is not interchangeable with bayonet-base or pin-base bulb types, even when wattage or voltage ratings are similar.