Why Won't My Tail Lights Turn Off?

If the tail lights are on when the vehicle is off, there could be a few causes depending on the vehicle, including a broken brake light switch or brake light switch stopper, faulty trailer light plug, or a broken wiring harness.

First, check if it's the tail lights or the brake lights. Learn the difference of the two here.

Broken Brake Light Switch or Stopper

If the brake lights are on when the vehicle is off, it's possible the brake light switch is still engaged. Many vehicles have a plastic stopper at the top of the brake pedal that disengages the switch when the brake pedal is stationary. Sometimes this plastic stopper breaks or shifts, which leaves the switch engaged and keeps the brake lights on.

Locate the switch near the top of the brake pedal underneath the dash. Have an assistant stand behind the vehicle. Check if the stopper is on the pedal. Press the brake pedal to gain access to the switch, and press button on the brake light switch.

If this does not turn the brake lights off or the button fails to depress all the way, the switch might need to be replaced. A short term solution to this problem is to disconnect the battery, but in order to access it later, this is not recommended if the hood latch is electric and not cable-operated.

If this turns the brake lights off, the stopper is probably not engaging the switch. Replace the stopper with a new one, or for a short term fix tape an item with similar width to the stopper like a coin. This should disengage the switch until the stopper is replaced.

Bad Trailer Light Plug

Sometimes trailer light plugs can corrode and cause the tail lights to stay on. First, confirm this problem does not happen with other lights on the tail light housing. Then, if your vehicle has a trailer light plug, disconnect the switch. If the tail lights turn off, the switch is likely faulty and the light plug assembly might need to be replaced.

Bad Wiring Harness

Sometimes the problem is from faulty wiring. Replacing a wiring harness is a possible DIY job that entails cutting the old connector off, stripping and twisting the wires and connecting the new switch with a splice connector. Check out the below video to learn more about replacing a faulty wiring harness yourself.