The Pontiac J2000 Sunbird uses an H4651 bulb size for high beam headlights and an H4656 bulb size for low beam headlights. The replacement chart covers 1984 to 1985 vehicle 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 Pontiac J2000 Sunbird uses H4651 sealed beam units for high beam headlights across the 1984-1985 model years, and H4656 sealed beam units for low beam headlights across the same period.
Both the H4651 and H4656 are ANSI-standardized sealed beam units recognized in the United States and Canada, measuring 4x6 inches in a rectangular form factor.
A sealed beam unit integrates the filament, reflector, and lens into a single non-serviceable assembly, meaning the entire unit requires replacement rather than an internal bulb.
Both the H4651 and H4656 operate at 12 volts, consistent with the standard electrical systems found in passenger vehicles of this type.
The H4651 and H4656 share the same physical housing size and ANSI classification framework but are designated for different beam functions and are not interchangeable with each other.
The shared 4x6-inch rectangular format across both beam types reflects a standardized fitment common to many North American vehicles of that era, though substitution between high and low beam positions is not supported by the specifications.