The GMC B7 front and rear turn signal bulbs both require a 1157 size bulb for proper operation. The replacement chart covers vehicle production spanning 1996 to 2002.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1157 bulb is the sole turn signal bulb type specified for the GMC B7 across both front and rear positions for the 1996-2002 model years.
The 1157 is a dual-filament bulb, meaning it contains two separate filaments within a single envelope, allowing it to serve two lighting functions at once, such as turn signaling and running light duties.
The 1157 operates on a 12-volt electrical system and draws 21 watts on its high-intensity filament and 5 watts on its low-intensity filament.
The 1157 uses a BAY15d bayonet base, which is an offset twin-pin base. The two pins are positioned at different heights to ensure the bulb is inserted in the correct orientation, preventing the filaments from being wired to the wrong circuit.
The 1157 conforms to ANSI standards and is recognized in both the United States and Canada, reflecting a standardized specification shared across North American automotive markets.
The front and rear turn signal positions on the GMC B7 share the same 1157 bulb specification across all listed model years, indicating interchangeability between those two positions.