Peterbilt 375 Back Up Light Bulb Size

The Peterbilt 375 back up light utilizes 1156 and P21W bulb sizes for illumination. Available data for the specified components covers the range from 1987 through 1996.

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
1993-1996	1156
1992	1156
1992	1156 (With 4 Rectangular Headlamps)
1991	1156
1990	1156
1990	1156 (With 4 Rectangular Headlamps)
1989	1156
1989	1156 (With Halogen Capsule Headlamps)
1988	1156
1987	1156
1987	1156 (With Halogen Capsule Headlamps)

Bulb Specifications

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

Other Locations

Additional Notes

The 1156 is the sole back up light bulb size specified for the Peterbilt 375 across all listed model years from 1987 to 1996.
The 1156 is an ANSI-standardized bulb type recognized in both the United States and Canada, operating at 12 volts with a 21-watt output.
As a single-filament bulb, the 1156 is designed to perform one lighting function, which aligns with its dedicated use in back up light applications.
The 1156 uses a BA15s bayonet base, a single-contact mount where the "s" denotes a single pin, distinguishing it from the dual-contact BA15d variant. These two base types are not interchangeable.
The 1156 is sometimes confused with the 1157, which shares the same BA15 bayonet shell but uses a dual-contact base for dual-filament operation. Substituting a 1157 in a 1156 socket is not compatible due to the differing base configurations.
For the 1990 and 1992 model years, the Peterbilt 375 has separate specification entries noting configurations with four rectangular headlamps, though both entries list the same 1156 bulb size for the back up light.
The 1987 and 1989 model years each carry an additional entry specifying a halogen capsule headlamp configuration, with the back up light bulb remaining the 1156 in both cases.