Brake lights not working
 

I have a 2003 and the right and left brake lights are not working. Checked bulbs, fuses with no luck. Suggestions clues???/

If both arent working at the same time, then its the fuse. And if you say the fuses are fine, then I'm willing to believe you. So it has to be a bad contact somewhere.

Try the hand brake (or however you call the brake that you use while parking the car). If that turns the lights on, then you might want to check the cables leaving your brake pedal. One of them might be disconnected.

Hand brake
 

tried the hand brake no change. I read another post on a chevy truck and it mentioned the brake light switch. My cruise has stopped working also. Won't engage at all. Didn't connect the cruise not working to the brake lights even though the brake switch does control both. Is this possible. If so is it difficult to change?

I think the left and rt hand side each have their own fuse...

Cruise will become inop- when it senses that brake lights arent working.

If you are measuring voltage at the brake switch. I believe there is an orange wire that will have 12v at all time, and a white wire that has 12 volts while the brake is depressed.
If the orange wire has no voltage, chack for a broken wire or blown fuse, if there is no voltage on the white wire when the brake is pressed, and the orange wire does have voltage, then the switch is bad.

The em

Do your brake light share the same bulb such as turn signal and running lights? If so and they are working then I would look into the brake switch as well.

thanks got confirmation it was the brake light switch but after replacing and using the cruise one time the brake lights went out again and the cruise does not work.

2002 ltz t blazer brake lites keep blowing bulbs any help please

I had a similar issue on my 03 TB several years ago and found there was a recall for this problem. I took it in and they replaced both sides. The problem started again a year or so later. I disconnected the battery and cleaned the sockets on both sides with alcohol. I had to replace a backup bulb about 6 months ago but no other issues.
I have not seen the issue the OP had but something is causing the circuit to draw to much current and I would suggest checking the connections on the brake light assemblies. I thought they used to much contact grease which is why I cleaned them with alcohol and did not put any back.

I have seen a number of Trailblazers (which years I don't know) which seemed to have the same progression of problems that my 2006 did.

First the left rear brake light went out. Several months later the right brake light went out. All the while, the top or cyclops light (whatever it's called) remained on.

I was told that the problem was switch inside the handle for the turn signal which also houses the cruise control.