I own a 06 trailblazer and iam putting in a brake controler in

First you need to have EBCM - electronic brake control module check for DTC'S - diagnostic trouble code's . If the light is on there is a code stored . I think most part stores can do this and for free . After you find out what code is stored , looking up that code in service repair information for diagnostic trouble shooting chart would be next step . There are a few codes too.
DTC C0035 or C0040
DTC C0045 or C0050
DTC C0110
DTC C0131
DTC C0161
DTC C0186
DTC C0196
DTC C0201
DTC C0240
DTC C0241 or P0856
DTC C0244 or P1689
DTC C0245
DTC C0283
DTC C0287
DTC C0290 or C0292
DTC C0455
DTC C0550
DTC C0558

Find the code do the diagnostic's , fix the problem , wiring issue's , a sensor , bad module ,what ever it is . The light will go out then . Here is a sample of code discription .
• DTC C0035 Left Front Wheel Speed Sensor Circuit
• DTC C0040 Right Front Wheel Speed Sensor Circuit

check cruise control fuse and check the brake lights see if brake light working because the brake light switch will deactivate cruise control when brakes is applied.if brake lights dont work either fuse blowed or switch bad.if all is good have vechicle code scan because cruise control control by PCM and vechicle speed sensor and thottle actuator control motor.

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.

please explain more fully exactly the problem as iam unsure here ,camper body ??? tried the earth wires ?? if i knew what i was dealing with i might have a better idea

If you have voltage you next have to have a ground please check that next,

This is a wear item.

check the brake light switch sensor on the brake pedals or replace the bulb...

what type controller did you install? Is this a camper or trailer? Is the controller hydraulic plumbed into master cylyder? Important to know how to adjust rheostat for sensitivity. If set at minimum the system is basically on the edge of not sending any signal to towed unit. The intructions should explain how to make this adjustment. If set too sensitive trailer brakes will lock up before the tow vehcle starts to brake. Controller should be set so trailer starts braking just befor the tow vehcle. If not the trailer will tax the tow vehicle brakes by pushing. Its set right when you feel the combination stretching out. trailer first then tow vehcle. Good luck and remember, if truck brakes first and too hard you risk a jacknife. All light voltages should be system voltage. Brake voltage is variable depending on setting on controller. Understand your breakaway brakes and how they work. breakaway breaks require an auxillary battery. Again, good luck and you know where to find me if I can be of anymore help.

Try to jack up the wheels and turn them to see if there is no seized brakes/calipers. Let us know how you get on.
Cheers

Your question is not clear, 2002 trailblazer has a towing harness, in order to find each wire, use a ohmmeter and try out each application.

In case of male harness of a camper you can test it with 12 volts in each wire looking which light is on and if it is different position cut wires and make similar wiring