Isuzu Impulse Back Up Light Bulb Size

The Isuzu Impulse back up light uses 1073 and P21W bulb sizes depending on the specific version of the vehicle. Available information covers the time range from 1983 to 1992.

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	P21W
1991	1073
1986-1990	P21W
1985	1073
1984	P21W
1983	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 P21W bulb is the most frequently specified back up light bulb for the Isuzu Impulse, appearing in seven of the ten model years covered by these specifications.
The P21W follows the ECE standard used in Europe and worldwide markets, operating at 12 volts with a 21-watt single-filament design and a BA15s bayonet base.
The 1073 bulb follows the ANSI standard used in the United States and Canada, operating at 12 volts with a 13-watt single-filament design and a BA15s bayonet base.
Both the P21W and the 1073 share the BA15s bayonet base type, meaning the physical mounting interface is the same across all ten model years in these specifications.
Despite sharing the same base type, the P21W and the 1073 differ in wattage, with the P21W rated at 21W and the 1073 rated at 13W, which reflects a meaningful difference in power draw and light output.
The 1073 is a lower-wattage variant of the 1156 bulb, meaning it shares the same ANSI family and base but is not electrically identical to the 1156 and should not be treated as a direct substitute for it.
The Isuzu Impulse (1983, 1985, and 1991) uses the 1073 bulb for the back up light, while the remaining model years from 1984 through 1992 use the P21W.
Because the P21W and the 1073 differ in wattage and regulatory standard, substituting one for the other is not supported by these specifications, even though both share the BA15s base.