Step by step repair guide on how to fix brake lights. Additional problems covered
in this section is how to repair a bulb that is dull or flickering. This article
pertains to all non-LED lighting systems.
Difficulty Scale: 3 of 10
Tools and Supplies Needed
Test light or voltmeter
Safety eyewear and gloves
Small screwdriver set
Begin with the vehicle on level ground, parking brake set while in park.
Step 1 - All non-LED brake lighting systems utilize a 12 volt bulb which
can fail. Visit -
Step 2 - A fuse is used to protect the brake light circuit
from amperage overload. If the fuse has failed it will not allow the electrical
current to continue to the brake lights. Visit -
testStep 3 - A control switch is used to connect the brake light
electrical circuit which is located near the brake pedal lever. Basic switches have
just two wires, power in and power out, and then onto the turn signal switch (American
cars only). Some cars are equipped with more than two wires integrated into the
brake light switch, a wiring schematic is needed locate the proper brake light circuit
wiring. Use a test light that is grounded, with the key in the "ON" position test
for power at one side (wire) of the switch, then press the brake pedal while testing
the opposite side (wire). The test light should illuminate if the switch is
good, if electrical power is good through the switch, go to the next step. If no
power is detected the switch has failed and replacement is required. If the brake
lights stay on continuously an adjustment of the switch is needed.
Step 4 - (American made cars only.) Both lower brake lights not working. Most
American cars are designed to have the brake light circuit wiring integrated into
the turn signal switch. The brake light bulb and the turn signal bulb are one and
the same, the turn signal switch interrupts the brake light circuit and installs
the blinker signal circuit when the turn signal switch is activated. If this switch
fails it will not allow the brake light signal through to the brake light wiring.
If brake light switch power is present at the turn signal switch but not at any
outgoing wires the turn signal switch has failed and replacement is required. A
wiring schematic can be helpful in testing the circuits.
Step 5 - Some cars are equipped with a body control module (BCM) or lighting
control module (LCM), this on-board computer controls lighting signals which can
malfunction not allowing the electrical current to continue to the brake light circuits.
Step 6 - Some Japanese cars such as Toyota, have a brake
light control module which is usually located in the trunk or near the rear seat
which can malfunction causing both lower or the center brake light to fail. Test
the incoming power feed from the brake light switch. If incoming power is present
without outgoing power replace the brake light control module.