My brake lights not working?

Good morning.

There is a brake light switch on top of the brake pedal under the dash. this is the most likely cause. This guide can help us fix it

https://www.2carpros.com/articles/brake-lights-not-working

Check your fuses as well to be sure there is not a bad one for the brake lights. Check out the diagrams (Below). Please let us know what happens.

Welcome, check the stop lamp fuse for voltage, use a testlite on the circuit, if you haven't already. Left instrument panel fuse block, 15 amp. Did you check voltage and ground at the rear?

Check fuse on the left side fuse block fuse #4, use only GM approved fuses, some aftermarket fuses can cause issues! also check your email for a pdf if the fuse isn't the problem.

Did you check the stop fuse see below

Hi, any fuses you check, use a testlite on the fuse circuit, to see if circuit is hot? Check the feed to and from the brake lamp switch. Should be close to brake pedal arm. Orange wire is voltage to the brake switch. When the switch is activated by stepping on the brake, the white wire goes hot and carries voltage to brake lites.

If the 3rd light works on the cab, the brake light switch is fine so save your time and trouble. There has to be a break in the wiring. Start at the light socket and follow the wiring until you find power. There are a couple plugs that attach to the wiring harness for the lights. Make sure they are not corroded or damaged.

If the cab light works, the brake light switch is fine. Check for power to the rear sockets as well as the wiring. Check for disconnected or broken grounds. Check for plugs for corrosion and make sure they are tight.

Let me know what you find.

Joe

There are 2 outputs for brake lights from brake light switch. One lights the third brake light. The other feed goes to the turn signal switch then to the rear lights. If your rear turn signals work then your problem is most likely the brake light switch. If not its your turn signal switch.

The center high mount (3rd) is powered differently and why it is working.

You can see where the power goes the the 3rd. So appearantly the white has power to the splice at the orange arrow. The blue arrow points to the t/s module.

The brake light switch may be bad?

I'm a little weak in the electrical dept. but the module, switch or a wire break would be my thoughts.

I believe that the brake and T/S bulbs are on two different circuits. It is hard to consider that both your brake bulbs would go at the same time along with your center high mount lamp too. So, start simple and check the fuse. Then check the brake light switch that is attached to the brake pedal. Look it over to make sure the plastic switch body is still intact and properly affixed to the brake pedal. The last thing (and most frustrating) could be a short circuit in the wiring. All you can do is test the wiring from source to end to try to locate the short or bad ground. Good luck.

Hi and thanks for using 2CarPros.com.

Based on what you replaced, I have to ask, did you check for a blown fuse? If not, check fuse 14 in the under hood fuse block. I have attached a picture of the fuse block which includes a legend of what each fuse is used for.

Also, here are a few links which discuss fuses, how to replace, how to use a test light, and how to check wiring. I included them because if the fuse is good, I need you to confirm there is power to and from the fuse.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

I hope this helps. Let me know if you have questions or need more information.

Take care,
Joe

Check and test the rear lamps junction block front of rear bumper on crossmember light blue wire for power if its not there you have an open wire between this point and the vehicle stop fuse 10amp

this guide will help you

https://www.2carpros.com/articles/brake-lights-not-working