1999 gmc sierra 1500 brake lights

There is a switch on the brake pedal, stick your head under the dash and follow the brake pedal up, you should see the switch pressed against a bracket, unplug the wires, one goes to the lights and the other should be live when the ignition is on, bridge the wires if the lights comes on then it needs a new switch, if there is power there and they still don't come on, check the bulbs?

Replace bulb

there usually are two brake switches on gmc's, one for the "third eye" or cab light and one for the rear brakes, look on the brace above the brake pedal for the second one, hint: the clip for the wires sometimes is loose or corroded, try taking it off and putting it back on (if the fuse is ok) first. other wise you will need to replace the switch.

There is a module on the frame near the back, passenger side.

Yes it is because if you have gotten 8 years out of two sets of rear break shoes you are doing well...........Emerg break is on the wear of the rear shoes............40 percent on the front and 60 percent on the front on aplication of the break.to change the application when towing u have to apply your parking break a little to change the ratio..........Hope this helps.

The brake light switch is at fault. Get a new one and replace it. The location is at the brake pedal area mounted on a bracket with a plunger stud that rest on the brake pedal's arm the pad is attached to

There's a switch at the top of your brake pedal. They wear out, chance are that's the problem, easy fix in the driveway.

have you replaced the bulbs?

Look up under dash where brake pedal pivots, you should see a switch that is activated by pedal arm.

Sounds like a rear end ratio problem ECM malfunction