Should you find that one brake light is not working on your car or truck, there are a few things you can check to find the cause. First,
check to make sure that it's not just a burnt out light bulb. You should also check to make sure no corrosion is present in the plug where
your brake light bulb plugs in. Gently wiggle the plug back and forth while someone is pressing down on the brake pedal and see if that
doesn't get the brake light working again. If that doesn't work, you need to check whether you have a bad ground or not. Run a jumper wire
from the ground on the brake light plug to a metal surface on your vehicle. If your brake light works, it's most likely a bad ground that is
causing your brake light to not work. Either reconnect the old ground wire or run a new ground wire. Most times you can track down the bad ground
without a wiring diagram. If you have difficulty finding the ground for the brake light, you may want to consult a service manual for your vehicle.
It should take you less than one hour to diagnose and make this repair, so don't let one brake light not working cause you any aggravation.