The GMC P6000 front and rear turn signal bulbs utilize 1157 or 2057 size specifications. The replacement chart covers 1983 to 1992 production years with corresponding bulb size data.
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 most widely used type across the GMC P6000 turn signal specifications, appearing in both the front and rear positions for the 1984-1992 model years (excluding 1991).
The 1157 is a dual-filament bulb rated at 12V with a 21W high-filament and 5W low-filament output, mounted on a BAY15d bayonet base, and is recognized under ANSI standards in both the US and Canada.
The dual-filament design of the 1157 allows a single bulb to serve two lighting functions, which in turn signal applications typically means the higher-wattage filament handles the active signal flash while the lower-wattage filament serves a secondary role such as a running or parking light.
The 2057 bulb is specified for the 1983 GMC P6000 in both the front and rear turn signal positions, making it the sole model year in these specifications to use that bulb type.
The 2057 shares the same BAY15d bayonet base and 12V operating voltage as the 1157, and is also an ANSI-standard dual-filament bulb, but operates at higher wattages of 26.9W and 8W on its respective filaments.
Because the 1157 and 2057 share the same BAY15d base, they are physically interchangeable in terms of socket fitment, though their differing wattage ratings mean electrical output will vary between the two types.
The higher filament wattage of the 2057 relative to the 1157 results in greater light output, which is a relevant distinction when considering replacement options between the two bulb types.
All turn signal bulb entries across both the front and rear positions of the GMC P6000 carry a Medium Duty classification, indicating a consistent duty rating throughout the specifications for this vehicle.