The Isuzu NPR uses 1157 and 1156 bulb sizes for front turn signal applications, with 1156 bulb size specified for rear turn signal positions. The replacement chart covers vehicle production spanning 1986 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 uses two bulb types across its front and rear turn signal positions: the 1157 and the 1156, both of which are ANSI-standardized bulbs common in the US and Canadian markets.
The 1157 is a dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d bayonet base. Its dual-filament design allows it to serve both a primary and a secondary lighting function within a single housing.
The 1156 is a single-filament bulb rated at 12V and 21W, mounted on a BA15s bayonet base. Unlike the 1157, it carries only one filament and is dedicated to a single lighting function.
The BAY15d base of the 1157 and the BA15s base of the 1156 are physically distinct. The BAY15d has offset locking pins to prevent incorrect installation, while the BA15s has a single-pin alignment. These two bulbs are not interchangeable despite their similar appearance.
On the Isuzu NPR, the front turn signal position uses the 1157 from 1995 through 2013, while the rear turn signal position uses the 1156 across the full 1986-2013 span covered by the specifications.
For the 1986-1994 model years, the front turn signal on the NPR (Heavy Duty) also used the 1156, meaning both front and rear positions shared the same single-filament bulb during that period.
A configuration change at the front turn signal position occurred between the 1994 and 1995 Heavy Duty models, where the bulb type shifted from the single-filament 1156 to the dual-filament 1157.
From 2002 onward, the specifications note a Tilt Cab designation for both front and rear turn signal positions, distinguishing those model years from the unlabeled entries covering 1996-2001.
Because the front and rear turn signal positions on the NPR use different bulb types from 1995 onward, the two positions require separate bulbs and cannot be serviced with a single part number across both locations.
The 1157 and 1156 are among the most widely used bulb types in North American automotive applications, and both operate on a standard 12V electrical system consistent with conventional vehicle architecture.