Brake switch

[tahoe.mkIII]

So I have been experiencing a weird drivability issue for the past year or so, mostly the torque converter locking and unlocking at random times while accelerating or cruising at speed. Thought it was a torque converter/trans issue figured I’d deal with it until I replace the power train in the near future…on the ride home yesterday a guy pulled up next to me and informed me that my brake lights were not working and were off or barely lit. I had a new brake switch on the shelf so I swapped it out when I got home. Brake lights working fine now, went on a test drive and the overdrive hiccup is gone. Turns out the pcm uses the brake switch data for torque converter lockup which makes sense, and was a satisfying surprise.

 

[someotherguy]

It's the brake switch but not literally the brake switch, if that makes sense. There are three sets of contacts in the switch - brake light, torque converter unlock, and cruise disable. Any of the three can break and usually only one will causing you to notice and replace the switch. Sounds like in your case, at least two sets broke. Pop the cover off it and have a look. You'll see how cheaply these are made, not that the price of a new one wasn't enough indicator..

Richard