Troubleshooting / No Brake Lights

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Why is One or All Brake Lights Out?

Introduction:

The brake lights on your car are designed to warn the drivers behind you that your car will be slowing down or stopping. Most cars are equipped with three brake lights, one on either side of the rear of the car and one on the upper level deck lid or roofline. The third light or Cyclops light was intergraded into the manufacturing process as an additional safety device in the early 1990's. A brake light system in most cases is a basic electrical system involving a simple positive and ground system controlled by switches activated by the driver/user. In all car electrical systems a fuse is used to protect the brake light electrical circuit. Most cars are equipped with a switch that is connected to the brake pedal lever or arm. The brake light switch rests in the open position and closed (electrical contacts connected) when the brake pedal is activated. The brake light switch is easily adjustable by moving the main switch housing within the metal bracket that holds the switch. Some brake light switches have additional functions such as the cruse control brake sensor and ignition key interlock function which do not affect the brake light function.

Brake Lights

A little know fact is the red brake lens can melt and distort when the brake lights are kept on for an extended amount of time. This heated condition can also negatively affect the brake light bulb holder as well. Never allow the brake light to stay on overnight.  There is one major difference between American and Japanese/European auto manufacturers. The American car makers have incorporated the brake light circuit into the turn signal system, and vice versa. The Japanese and European manufacturers design the brake and turn signal electrical systems separately. For this reason troubleshooting the same problem will be slightly different from the two different styles of manufacturing. We have listed "American" and "Japanese/European" separately in the page below. We also include procedures for one to all brake lights not working. One other condition that we will cover in this section is how to repair a brake light bulb that is dull or flickering.

Troubleshooting Procedures - Read Completely Before Beginning

(American Car) All Brake Lights Not Working

• Check System Fuse: 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. To check the fuse, first locate the brake light system fuse in the fuse panel which is either under the dash or under the hood in the power distribution center. Connect the test light to a ground like an engine or dash bracket and turn the ignition key to the "on" position. Using the test light probe both sides of the fuse. If the test light illuminates on both sides the fuse is ok continue onto the next step. If one side of the fuse illuminates the fuse has failed and needs to be replaced. If the fuse fails as soon as it is replaced or when you apply the brake pedal the brake light electrical circuit is shorted to ground. Rarely a system short can occur, a car repair manual is needed to find the wiring schematic for the brake light circuit. Once the brake light wiring has been located inspect and repair as needed.
   
• Check Brake Light Bulbs: All cars have three brake light bulbs that create the brake light illumination affect. If all of these brake light bulbs fail no brake light operation will occur. I know what you're thinking, you might say all three brake lights at once? But in reality one brake light went out at a time and you did not notice. People only tend to notice something when they almost run into the back of your car to help persuade them to inform you the brake lights aren't working. Remove any of the brake light bulbs to confirm the bulb is ok or burned. After the bulb has been removed inspect the filament and replace if failed. If the brake light bulbs are ok continue to the next step.
   
• Checking the Brake Light Switch: A control switch is used to connect the brake light electrical circuit. This switch is located near the brake pedal lever. Basic switches have just two wires, power in and power out to the turn signal switch. Use a test light that is grounded and 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). It should illuminate the test light, if electrical power is connected through the switch go to the next step. If no power is detected through the switch the brake light switch has failed and replacement is required. If your car is equipped with more than two wires integrated into the brake light switch a car repair manual is needed to locate the proper brake light circuit wiring.
  

(American Car) Both Lower Brake Lights Not Working

• Check Brake Light Bulbs: All cars have three brake light bulbs that create the brake light illumination affect. If the lower two bulbs fail no lower brake light operation will occur. I know what you're thinking, you might say two brake lights at once? But in reality one brake light went out at a time and you did not notice. People only tend to notice something when they almost run into the back of your car to help persuade them to inform you the brake lights aren't working. Remove either of the brake light bulbs to confirm the bulb is ok or burned. After the bulb has been removed inspect the filament and replace if failed. If the brake light bulbs are ok continue to the next step.
   
• Checking the Turn Signal Switch: Most American cars are designed to have the brake light switch wiring intergraded into the turn signal switch. Because 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. To test for this condition a car repair manual is needed to test incoming and outgoing electrical current. If brake light switch power is present at the turn signal switch but not at any outgoing brake light wires the turn signal switch has probably failed.

 
(American Car) One Brake Light Not Working

• Inspect Brake Light Bulb: The number one reason for a brake light operation failure is a failed brake light bulb. To check this condition access the bulb by removing the rear cover located in the trunk or rear compartment. Some cars allow you to remove the entire brake light lens to retrieve the brake light bulb. Once the bulb has been removed inspect the bulb filament. If it looks broken or if the bulb is smoked the bulb needs to be replaced. If you have replaced the bulb but it still doesn't work remove the bulb. With the key in the "on" position have someone hold their foot on the brake pedal and use a grounded test light to carful test the terminals inside the light socket. One of the terminals should illuminate the test light. (Note: Do not touch the outer metal ring that holds the bulb in place for it is grounded and can blow the system fuse if connected to the inner terminals.) If the test light illuminates reinstall the brake light bulb. While the brake pedal is depressed test the outer metal ring that holds the bulb, if power is present the ground lead from the light socket is bad. If the outer ring does not illuminate the bulb has failed and replacement is required.
   
  
• Scan BCM for Trouble Codes: Some cars are equipped with a body control module or BCM this onboard computer controls and lighting signals and can malfunction not allowing the electrical current to continue to the brake light circuits. This condition is rare but it can happen. If you have performed all of the tests above and all results are positive scan the BCM for trouble codes if no codes are present try replacing the BCM.

(Japanese/European) All Brake Lights Not Working

• Check System Fuse: 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. To check the fuse, first locate the brake light system fuse in the fuse panel which is either under the dash or under the hood in the power distribution center. Connect the test light to a ground like an engine or dash bracket and turn the ignition key to the "on" position. Using the test light probe both sides of the fuse. If the test light illuminates on both sides the fuse is ok continue onto the next step. If one side of the fuse illuminates the fuse has failed and needs to be replaced. If the fuse fails as soon as it is replaced or when you apply the brake pedal the brake light electrical circuit is shorted to ground. Rarely a system short can occur, a car repair manual is needed to find the wiring schematic for the brake light circuit. Once the brake light wiring has been located inspect and repair as needed.
   
• Check Brake Light Bulbs: All cars have three brake light bulbs that create the brake light illumination affect. If all of these brake light bulbs fail no brake light operation will occur. I know what you're thinking, you might say all three brake lights at once? But in reality one brake light went out at a time and you did not notice. People only tend to notice something when they almost run into the back of your car to help persuade them to inform you the brake lights aren't working. Remove any of the brake light bulbs to confirm the bulb is ok or burned. After the bulb has been removed inspect the filament and replace if failed. If the brake light bulbs are ok continue to the next step.
   
• Checking the Brake Light Switch: A control switch is used to connect the brake light electrical circuit. This switch is located near the brake pedal lever. Basic switches have just two wires, power in and power out to the brake light wiring system. Use a test light that is grounded and 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). It should illuminate the test light, if electrical power is connected through the switch go to the next step. If no power is detected through the switch the brake light switch has failed and replacement is required. If your car is equipped with more than two wires integrated into the brake light switch a car repair manual is needed to locate the proper brake light circuit wiring.
  

(Japanese/European) Both Lower Brake Lights Not Working

• Check Brake Light Bulbs: All cars have three brake light bulbs that create the brake light illumination affect. If all of these brake light bulbs fail no brake light operation will occur. I know what you're thinking, you might say both brake lights at once? But in reality one brake light went out at a time and you did not notice. People only tend to notice something when they almost run into the back of your car to help persuade them to inform you your brake lights aren't working. Remove either of the brake light bulbs to confirm the bulb is ok. After the bulb has been removed inspect the filament and replace if failed. If the brake light bulbs are ok continue to the next step.
   
• Checking Brake Light Control Module: Some Japanese cars have a brake light control module that can malfunction causing both lower or the center brake light to fail. To check for this condition locate the module which is usually near the rear seat on the driver's side. Then test the incoming power feed from the brake light switch. If incoming power is present without outgoing power replace the brake light control module with new to recheck system.

(Japanese/European) One Brake Light Not Working

• Inspect Brake Light Bulb: The number one reason for a brake light operation failure is a failed brake light bulb. To check this condition access the bulb by removing the rear cover located in the trunk or rear compartment. Some cars allow you to remove the entire brake light lens to retrieve the brake light bulb. Once the bulb has been removed inspect the bulb filament, if it looks broken or if the bulb is smoked the bulb needs to be replaced. If you have replaced the bulb but it still doesn't work remove the bulb. With the key in the "on" position have someone hold their foot on the brake pedal and use a grounded test light to carful test the terminals inside the light socket. One of the terminals should illuminate the test light. (Note: Do not touch the outer metal ring that holds the bulb in place for it is grounded and can blow the system fuse if connected to the inner terminals.) If the test light illuminates reinstall the brake light bulb. While the brake pedal is depressed test the outer metal ring that holds the bulb, if power is present the ground lead from the light socket is bad. If the outer ring does not illuminate the bulb has failed and replacement is required.
   
• Scan BCM for Trouble Codes: Some cars are equipped with a body control module or BCM this onboard computer controls and lighting signals and can malfunction not allowing the electrical current to continue to the brake light circuits. This condition is rare but it can happen. If you have performed all of the tests above and all results are positive scan the BCM for trouble codes if no codes are present try replacing the BCM.

Brake Lights Dull or Flickering - All Cars

• Dull or Dim Brake Light Repair: If your car has a dull or dim brake light it is dangerous to you and other drivers. A dim brake light is a mystery to most people because the bulb is working, just not correctly. First confirm a new and correct brake light bulb has been installed. Next, turn the ignition key to the "on" position and have a helper depress the brake pedal. With the bulb installed touch a grounded test light to the outer bulb holder ring. If the bulb brightness changes the bulb socket ground has high resistance and needs to be repaired or replaced.
   
• Flickering Brake Light Bulb Repair: A flickering brake light bulb can be very distracting and annoying. A brake light flickers because the power or ground is being obstructed momentarily. The most common cause for this condition is a loose fitting bulb socket. To check for this condition remove the brake light bulb in question, while a helper hold their foot on the brake pedal move the bulb around slightly in the socket. If the bulb flickers replace or repair the bulb socket as needed to regain proper brake light bulb operation. If the brake light bulb socket tests ok wiggle the brake light fuse and wiring at the brake light bulb socket, brake light switch and turn signal switch (American cars). If the brake light bulb flickers repair the component or wiring as needed.

Preferred Procedure: Always replace brake light bulbs with manufacturers recommend replacement bulbs. If you cannot find the correct replacement bulb part number consult an Auto Part Store for additional manufacturer information.

Common Problems

• When brake light bulbs are replaced with the incorrect bulb causing no or dim brake light operation
• If the brake lights stay on continuously it could mean the brake light switch has failed or an adjustment is needed

Troubleshooting / No Brake Lights

• Purchase Test Light
• Purchase Brake Light Bulbs

Check Manufacturer Specific Car Brake Light Questions

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