2004 Chevrolet Trailblazer brake light doesn't work

Tony, our TB's only have 3 bulbs, 1 brake, 1 running, 1 backup.
If you happened to be playing with NEW LED bulbs (from local retail location) for the brakes, guaranteed you blew the fuse under the rear seat. It takes a special CK socket for the brakes that no one carry's. If you're only dealing with normal incondecent bulbs, I'd still check the fuse under the rear passenger seat.

There was a recall on this, see your local Chevrolet dealer.... Recall Date: NOV 01, 2004 Model Affected: 2003 Chevrolet Trailblazer Summary: ON CERTAIN SPORT UTILITY VEHICLES, VIBRATION AND HEAT MAY CAUSE THE TAIL LAMP/STOP LAMP BULB TO LOOSEN IN ITS SOCKET. IF THIS OCCURS, THE BULB MAY FLICKER AND EVENTUALLY BECOME INOPERATIVE. Consequences: AN INOPERATIVE BRAKE LAMP WILL NOT CONVEY THE DRIVER'S INTENTION OF STOPPING TO DRIVERS IN FOLLOWING VEHICLES, AND AN INOPERATIVE REAR TURN SIGNAL LAMP WILL NOT CONVEY THE DRIVER'S INTENTION TO TURN TO DRIVERS IN FOLLOWING VEHICLES. BOTH OF THESE FAILURES CAN INCREASE THE RISK OF A CRASH. Remedy: DEALERS WILL INSPECT THE TAIL LAMP/STOP LAMP ASSEMBLIES, AND IF NECESSARY, REPLACE THEM. THE RECALL BEGAN ON NOVEMBER 22, 2004. OWNERS SHOULD CONTACT CHEVROLET AT 1-800-630-2438, OLDSMOBILE AT 1-800-630-6537, BUICK AT 1-866-608-8080, OR GMC AT 1-866-996-9463. Potential Units Affected: 871473 Notes: GENERAL MOTORS CORP. Read more: http://www.motortrend.com/cars/2003/chevrolet/trailblazer/recalls/#ixzz2jWJ1eDyR

I would start by trying another bulb. Even though the brake and tail light share the same bulb they actually are powering different filaments inside of the bulb so you can have a tail light filament that is working fine and illuminating properly but have a burned out brake light element that won't work at all...all inside the same bulb. Not uncommon at all to see this problem and these bulbs are pretty inexpensive.

brake light switc faulty

Check fuse #34 in the fuse panel located under rear seat.

check the ground wire, possibly in the back behind one of the access panels near the wiring harness

If this is a trailblazer check all the other bulbs in the rear you probably have more than one bad bulb. Chech the bulbs for slight blackaning (flash).

This is known problem, and it is the turn signal switch.

I have the same problem with my 2004 Trailblazer LT. Driver side brake light does not illuminate. All other lights work fine. Replaced bulbs. Still does not illuminate. Cannot figure out which fuse goes to this light. Could it be a fuse?

Hi, check for bad bullbs and dirty contacts inside the bulb sockets ...