GMC Sierra Map Light Bulb Size

Additional Notes

• The 212-2 and 578 are both festoon-type bulbs sharing a 41mm length and identical 12V, 12W electrical ratings, making them physically similar in size and power draw despite having different base configurations.
• The key distinction between the 212-2 and 578 lies in their contact design. The 212-2 uses an SV8.5 base, which features a central barrel-style socket mount, while the 578 uses end-cap contacts, where the electrical connection is made at each flat end of the bulb.
• Because the 212-2 and 578 differ in base type, they are not interchangeable, even though they share the same physical length and wattage.
• The 168 is a T10 miniature wedge bulb rated at 12V and 4.9W, a significantly lower wattage than either festoon type used in later model years of the GMC Sierra.
• All three bulb types, the 212-2, 578, and 168, conform to ANSI standards recognized in both the United States and Canada.
• The GMC Sierra used the 212-2 bulb for map lighting across the 2007-2013 model years, representing the longest continuous span of a single bulb type in these specifications.
• For the 2014 GMC Sierra, the 212-2 bulb size applies exclusively to the 3500 HD variant, indicating that not all 2014 Sierra configurations share the same map light fitment.
• The 578 bulb was used across the 2001-2006 model years, serving as the transitional festoon type between the earlier wedge-style 168 and the later SV8.5-based 212-2.
• The 1999-2000 model years used the 168 wedge bulb, which operates at a notably lower wattage than the festoon bulbs specified for all subsequent years in these records.