if you remove one on the lamps it will have some small print on the base of the bulb it may be both numbers and letters, but this will be the part number you are looking for and you can buy replacements at just about any automotive parts store.
twist and pull out
A 2008 Chevy Tahoe uses a standard 9005 size light bulb. Bulbs are designed to last for many years and rarely require replacement.
See sources and related links below for 1999 Chevrolet Tahoe light bulb part number list.
try new light bulbs
How do you replace a break light switch on 1995 Chevy Tahoe
Check the bulbs and then the multifunction switch (headlight switch)
pull the two rods from the top of the light assembly after raising the hood, this allows you to swing the assembly out and put the new bulbs in
If you are asking about the high beam headlights you either have burned out bulbs or the switch that turns the high beams on has failed. If you are asking about the high beam indicator on the dash I would also think it no longer works account it has failed.
the inside bulbs are the high beams.
I think you have a faulty light switch or relay, if the bulbs / wiring are ok.
The # is 1157 bulbs.
how do I replace interior light bulbs in 2002 chevy impala. I removed the cover, but the bulb is cramped in and I can't pull it out.