GMC P6000 Back Up Light Bulb Size

The GMC P6000 back up light requires a 1156 bulb size for the specific lighting component located at the rear of the vehicle. Available data covers the span from 1983 through 1992 for the mentioned automotive application.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1992	1156 (Medium Duty)
1983-1990	1156 (Medium Duty)

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The GMC P6000 back up light bulb specification calls for the 1156 across the 1983-1992 model years, with the trim level noted as Medium Duty throughout.
The 1156 is an ANSI-standardized bulb recognized in both the United States and Canada, making it a widely distributed and regulated part type.
As a single-filament bulb, the 1156 serves one dedicated electrical function, which in this application is the back up light circuit.
The 1156 uses a BA15s bayonet base, a single-contact mount where the "s" designation indicates a single locating pin on the base collar.
The bulb operates at 12 volts and draws 21 watts, consistent with standard automotive electrical systems of that era.
Because the 1156 is a single-filament type, it is not interchangeable with the visually similar 1157, which carries a dual-filament design and a BA15d double-contact base.