Isuzu FTR front side marker bulbs use 168 or 89 size, while rear side marker bulbs use 89 size. The replacement chart covers 1988 to 2011 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Isuzu FTR uses two distinct bulb types across its front side marker positions: the 168 and the 89, both conforming to ANSI standards applicable in the US and Canada.
The 168 bulb is a T10 miniature wedge type rated at 12V and 4.9W, making it a low-wattage lamp suited for marker and clearance lighting applications.
The 89 bulb uses a BA15s single-contact bayonet base and is rated at 12V and 13W, drawing considerably more power than the 168 and belonging to the same bulb family as the 1156, though at a lower wattage.
The front side marker position on the Isuzu FTR (Heavy Duty) transitioned from the 89 bulb to the 168 bulb between the 1994 and 1995 model years, meaning the two types are not interchangeable across that boundary despite both serving the same position.
Front side marker fitment for the Heavy Duty configuration specifies the 168 bulb for model years 1995-2001 and the 89 bulb for model years 1988-1994.
The Tilt Cab configuration, covering model years 2006-2011, exclusively uses the 168 bulb in the front side marker position.
The rear side marker position is specified only for the Heavy Duty configuration and exclusively uses the 89 bulb across model years 1988-1994.
The wedge base of the 168 and the BA15s bayonet base of the 89 are physically incompatible socket types, so the two bulbs cannot be substituted for one another regardless of wattage considerations.