Chevrolet P40 Back Up Light Bulb Size

The Chevrolet P40 back up light utilizes a single 1156 bulb size for the lighting component. Available data for the specified vehicle covers the range from 1979 through 1988.

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
1979-1988	1156

Bulb Specifications

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

Other Locations

Additional Notes

The Chevrolet P40 uses the 1156 bulb for the back up light across all listed model years, spanning 1979-1988.
The 1156 is an ANSI-standardized bulb type recognized across the United States and Canada, meaning it conforms to a defined set of electrical and physical characteristics shared by all compliant manufacturers.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard automotive reverse lighting applications.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, as opposed to dual-filament types that handle two functions such as braking and running light simultaneously.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a single-contact bayonet fitting with a 15mm base width, a common automotive socket type.
The BA15s single-contact base of the 1156 is not interchangeable with the BA15d double-contact base found on dual-filament bulbs such as the 1157, despite the similar physical size of the two base types.