The Isuzu Impulse brake light requires a 1157 bulb size for proper installation and function within the rear lighting assembly. Available data covers the production range from 1983 through 1992 for the specified vehicle components.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Isuzu Impulse uses the 1157 bulb for the brake light position across the full 1983-1992 model range covered by these specifications.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21W/5W output. The dual-filament design allows a single bulb to serve both a lower-intensity running function and a higher-intensity braking function.
The BAY15d bayonet base features two offset pins, which physically prevent incorrect single-filament bulbs from being seated in the socket. Substituting a single-filament bulb in a dual-filament application would result in loss of one lighting function.
The center high mount stop light on the Isuzu Impulse uses one of two miniature wedge bulbs depending on the model year, making it the only position in these specifications where a bulb change occurs across the production run.
The 1988-1992 Impulse center high mount stop light takes a 194 bulb, while the 1983-1987 model years use a 168 bulb. Both are T10 miniature wedge bulbs operating at 12V, so they share the same physical base type.
Although the 194 and 168 share the T10 wedge form factor, they differ in wattage. The 168 is rated at 4.9W and the 194 at 3.78W. This difference means the two bulbs are not rated as interchangeable replacements for one another despite fitting the same socket physically.
All three bulb types listed in these specifications, the 1157, 194, and 168, conform to ANSI standards applicable in both the United States and Canada.
The 1157 operates at a significantly higher wattage than either wedge bulb used in the center high mount position. At 21W on its high filament, it produces considerably more light output, consistent with its role as the primary brake signal at the rear of the vehicle.