GMC P6000 front and rear side marker bulbs utilize 1157 and 194 bulb sizes for optimal illumination. The replacement chart covers 1983 to 1992 production years with corresponding size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC P6000 front and rear side marker positions draw from two bulb types across the listed model years: the 1157 and the 194, both of which conform to ANSI standards recognized in the United States and Canada.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with filaments drawing 21W and 5W respectively. Its dual-filament design distinguishes it electrically from the single-filament 194.
The 194 is a miniature wedge bulb in the T10 form factor, rated at 12V and 3.78W. Its wedge base differs structurally from the bayonet base of the 1157, making the two types non-interchangeable without a socket adapter.
Because the 1157 and 194 use different base types and wattage ratings, substituting one for the other in a socket designed for the opposite type is not supported by these specifications.
On the GMC P6000, the front side marker position for 1983-1984, 1986-1987, and 1989 Medium Duty trims without the two-rectangular-headlight configuration takes the 1157 bulb.
The front side marker position for 1983-1988 Medium Duty trims equipped with two rectangular headlights takes the 194 bulb, indicating that headlight configuration is a determining factor in front marker bulb fitment for those years.
The rear side marker position across the listed years is served predominantly by the 194 bulb, with the 1157 appearing only in the 1987 Medium Duty rear application.
The 1988 front side marker row carries no trim qualifier beyond the year itself, while the 1988 rear side marker is designated Medium Duty, reflecting that the two positions for that year are specified under different conditions.
The 1990 and 1992 front and rear side marker positions each use the 194 bulb under the Medium Duty designation, with no alternative fitment listed for those years.
The 1985 front side marker row lists the 194 bulb without a trim qualifier, whereas the 1985 rear side marker row carries the Medium Duty designation, distinguishing the two positions for that model year.