Ferrari Testarossa Back Up Light Bulb Size

The Ferrari Testarossa back up light requires bulb size 1073 or P21W depending on the specific version of the component. Data for the lighting specifications covers the range from 1985 to 1989.

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
1989	P21W
1985-1988	1073

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	1073

Other Locations

Additional Notes

The Ferrari Testarossa backup light specifications cover the 1985-1989 model years, with two distinct bulb types appearing across that span.
The 1073 is an ANSI-standard single-filament bulb rated at 12V and 13W, fitted with a BA15s bayonet base, and it serves the backup light position on the 1985-1988 Testarossa.
The P21W is an ECE-standard single-filament signalling bulb rated at 12V and 21W, also using a BA15s bayonet base, and it is specified for the 1989 Testarossa.
The 1073 is noted as a lower wattage variant of the 1156 bulb. At 13W versus the 21W of the P21W, the 1073 produces noticeably less light output.
Despite the wattage difference between the 1073 and P21W, both bulbs share the BA15s bayonet base, meaning the physical socket type is consistent across all five model years covered.
The ANSI 1073 and ECE P21W represent different regional standards. The shift to the P21W in the 1989 model year reflects a move toward European-market bulb standardization for that position.
Although the BA15s base is shared between the 1073 and P21W, substituting one for the other is not indicated as interchangeable in these specifications, as the wattage ratings differ by 8W.