The Isuzu NPR-HD uses a 1157 bulb size for the front turn signal and a 1156 bulb size for the rear turn signal. The replacement chart covers vehicle production spanning 1999 to 2013.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Isuzu NPR-HD uses the 1157 bulb for the front turn signal across all Tilt Cab configurations from 1999-2013.
The 1157 is a dual-filament bulb, meaning it serves two lighting functions within a single housing. It operates at 12V with filament ratings of 21W and 5W, and it seats into a BAY15d bayonet base.
The BAY15d base features two offset pins at different heights, a design that prevents incorrect insertion and ensures the two filaments are connected to their respective circuits.
The rear turn signal on the Isuzu NPR-HD Tilt Cab calls for the 1156 bulb across the same 1999-2013 model range.
The 1156 is a single-filament bulb rated at 12V and 21W, mounted on a BA15s bayonet base. The BA15s base uses two pins at the same height, distinguishing it physically from the BAY15d used by the 1157.
Although the 1156 and 1157 share the same 21W main filament rating and a visually similar bayonet form, their bases are not interchangeable. The offset-pin BAY15d socket of the 1157 application will not accept the single-filament BA15s base of the 1156, and vice versa.
Both the 1156 and 1157 are defined under ANSI standards and are recognized across the United States and Canada, placing them within a widely standardized bulb classification system.
All turn signal bulb specifications listed apply exclusively to the Tilt Cab body configuration of the NPR-HD.