I started having issues with my Tahoe recently where the brake lights would come on just fine but as the pedal further depressed they would go out. I went the cheap route first swapping out the brake light switch. That did not work. Then I dug a little deeper and changed out the turn signal multi switch. That did not work. Any ideas?

Also, where is a good place to get some wiring diagrams?

I would check the tail light circuit boards. See if your getting power to the connector. The circuit boards are knowned for going bad. Is it all the brake lights. The third brake light dosent go though the multi function switch.

It is all three brake lights so I don't think it'* the tail light circuit boards. I'm wondering if there is an issue with the wiring from the brake light switch beyond. There has to be something in series to cause all of them to drop out simultaniously, right? I'm no car wiz so I'm grabbing at straws.

Thanks for the info

i would still suspect something in the brake petal switch area, if its all three, look and see if there is some adjustment or weird bracket thing going on

I have a feeling that they're not going out the farther the pedal is depressed, more like they're going out the longer they are on. This would need to verified of course.

Does their happen to be a relay in that circuit? If so, I'm betting something is shorted and causing that circuit to heat up, and the relay then disengages shutting everything off. After it cools down, the lights can come back on again.

I think i found the problem, now I just need to go through the fun process of deconstruction...again. I'm almost positive I have loose wires in my brake light switch harness. I popped the brake light switch off the pedal shaft relieving any tension on the harness and the brakes are working consistantly without fail. I hope this is it because it'* simple and cheap to find and fix a wire connection.

update. after pulling out the harness it was indeed a broken neutral wire. sneaky guy was hidden in unfazed insulation. I couldn't find anyone local with the right connector to replace the wire so I soldered and heat shrinked it. Hope this helps someone else that stumbles across this post having the same problem. Thanks again everyone for their help.

thats a good one