Just noticed this tonight, hope it hasn't been going on long.

1998 Silverado pickup, extended cab with 3rd door.

I knew I had one backup light out. I removed the tail lens, snapped a new bulb in, and the backup light worked. Like I always do when I replace a bulb back there, I went through all the lights to make sure they all worked.

NO brake lights work. Not the tail, and not the 3rd brake light.
I checked all the bulbs, even the ones in the 3rd light, (swapped in new bulbs and checked the old ones with an ohmmeter).

Checked fuse #1 on the inside fuse panel - it is good.
The backup, turn signal, parking lights and hazards all work fine.

Reading up, it seems like if it were the stop light relay or the large Aux Fuse #2 on the underhood panel, the tail brake lights would not work, but the 3rd light would because it is fed directly off the brake pedal stop light switch.
Correct?

So.... I am assuming I have a bad stop light switch at the brake pedal.
Reasonable?

Now, if somebody could give me some idea of what the stop light switch really truly looks like under the dash on the brake pedal, and how the heck I would get it out, I would really appreciate it. Man, it sure does appear to be a much bigger pain than the simple plastic gizmo on my old '72 Olds Cutlass!

Does not seem likely that it's the turn signal switch in the column, since the 3rd light doesn't work either.

Your assessment sounds correct as to the stop switch. Good job.

My '98 C/K manual says this:

1. Disconnect batt ground.
2. Remove the snap ring on the pin of the pedal that the switch is mounted on.
3. Unsnap the switch from the pushrod and remove.
4. Reverse the order using a 7/16 socket to install the snap ring.

Good luck.

Thank you.

Yes, I've seen that description of how to replace the stop light switch many times, but it means nothing to me. When I look above the brake pedal, I don't see anything that looks like a switch or a snap ring.

I have also read many conflicting reports that say it is very hard to get the switch out, even talking about removing bolts and lowering the steering
column, which I do not understand at all.

If only somewhere there were some labeled photographs of what the heck
is under there, I think I could do it.

If you don't see it- it may be missing-- I know it is way up there-- it may be dangling or shoved aside-- look for the wiring connector-- has at least one orange (battery hot) and the white (brake light switch) wires in it....hope this helps- meanwhile I'll look for a photo

OK. Just got back from crawling under the dash of my '98 sub. The switch is white and above the steering column. It looks like a real pain in the wrist to change out but I was able to reach up and around and touch the whole thing.

The 2 problems I see are getting the retaining ring off and then getting the wiring connector off since there is room for only one hand.

777Stickman... THANK YOU for doing this for me. I will check it out tomorrow
and see if I think I can get my hand up there to get it out.

Thank you again.

Well, it is way high up in there. It is freezing cold here in Pennsylvania, and I do not have an indoor place to work on cars. So... having diagnosed it enough to be reasonably sure it was just the switch, I took it to the place I usually get work done when I have to (which is, amazingly, a dealership - they do excellent work, always on time, always fixed right --- yes, those do exist!)

Anyway, it was just the switch. I had to pay about 12 bucks for a part and for 1 hour of labor, but that seems reasonable.
He said, yes, it's a rough one to get out, but some are worse. There was one model that they take bets on how many cuts and how much blood the poor guy will have by the time he gets done changing it. The '98 Silverado
ain't one of those!