Brake lights not lighting when brake pedal is pressed on a 2002 trailblazer right and left side not working (new bulbs) top light on hatch lid is the only one that lights

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's a harness that runs from the rear body into the hatch, through a rubber tube. These wires break with age and movement.

Remove the hatch brake light and verify that the unit is getting +12v when the brake pedal is pressed. If so, connect +12v + Ground to the brake light directly, and see if it works. If not, you have a ground issue (usually corrosion) the brake light. Look for the ground connection in the hatch harness.


Repairing the hatch harness is doable, and easier than replacing the whole harness.

Could be a bad ground in the brake wiring. If you make a ground from the socket to the frame or body, see if the lights work.

Make sure the socket has a proper ground and a good bulb. There should be power at the socket only when the pedal is pressed.

I think you either have a defective bulb socket or you still have a ground problem, that is the only thing that can cause this, the ground issue may be caused by the turn signal switch as well.

Check your fuses if it isn't that check and see if your bulbs are blown.

check the fusse for the brake ligt and the righht and left rear lights. also check the brake switch white is located underneath the dash board an over the brake pedal

Open the full hatch.
Pull down the weather strip near the rear dome light.
There should be a wire with a connector in it. Disconnect it
Close the full hatch.

Open just the window hatch. There is 1 screw on either side of the bulb housing.

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?

Igot the same problem on left side.The problem was the convertor for the trailler plug.