Acura TLX Brake Light Fail - How To Troubleshoot

By Nick Marchenko, PhD

Experiencing a brake light failure in your Acura TLX can be more than just a nuisance—it's a safety issue that demands immediate attention. Combining insights from various threads and discussions, this guide aims to provide you with a comprehensive DIY approach to diagnosing and fixing brake light issues in your Acura TLX. Whether you're facing a complete brake light failure, issues with the shift lever lock, or problems related to the brake pedal position switch, this guide has you covered.

Diagnosing the Problem

Before diving into repairs, it's crucial to understand the root cause of your brake light failure. Start by:

• Checking both the STOP (20A) under-hood fuse and the Fuse 9 (7.5A) located under the driver's dash. Ensure both fuses are in good condition.
• Testing for power at the Brake Pedal Position Switch. The WHT/YEL wire should have 12v, and the WHT/BLK wire should show 12v when the brake pedal is pressed.
• Inspecting the power supply to the Brake Light Failure Sensor in the left taillamp housing. If the WHT/BLK wire does not have power when the brake pedal is pressed, this indicates a potential open in the wiring.
• Start with the most simple task - inspect the brake light bulbs. If the problem lies with them - a simple replacement will be the most budget-friendly solution. Make sure you are using the correct bulbs before installation - check out our bulb size chart to ensure the correct fitment.

Acura TLX Bulb Size Chart:

• 2022;
• 2021;
• 2020;
• 2019;
• 2018;
• 2017;
• 2016;
• 2015;

Troubleshooting Tips

Upon identifying the problem areas, follow these steps for a more detailed investigation and fix:

• If there's no power to the Brake Light Failure Sensor, consider checking the continuity and connections at every splice/connector from the Brake Pedal Position Switch to the sensor.
• Examine the Shift Interlock functionality, which might not work if there's an electrical issue. The interlock switch could be failing to receive power.
• For wiring issues, particularly with the WHT/BLK wire, trace the path for any signs of damage or disconnection. Remember, this wire does not pass through the PCM but directly affects the brake light and shift lock system.

Practical Fixes

Based on the collected advice, here are steps to rectify the identified issues:

• If a fuse is blown, replace it with a new one of the same rating.
• For a faulty Brake Pedal Position Switch, replacing the switch could resolve the issue.
• Should there be a wiring issue, consider bypassing the damaged section with a new wire of appropriate gauge, ensuring solid connections either by soldering or using quality connectors.
• In case of damaged connectors, particularly if the wire and terminal have melted causing an open, seek a replacement connector and splice in all necessary wires carefully.

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Remember, while DIY fixes can save money and offer a rewarding experience, safety should never be compromised. If you're unsure about any step or if the problem persists, consulting a professional is advised.

See Also:

Expand your knowledge on maintaining your Acura TLX by exploring related topics:

• Fixing Acura TLX CarPlay Not Working
• Changing the Battery in Your Acura TLX
• Replacing 2015 Acura TLX Headlight Bulb
• A Guide to Acura TLX Dash Warning Lights

By following this guide and utilizing the resources provided, you can confidently tackle brake light issues in your Acura TLX, ensuring your vehicle remains safe and functional on the road.

Nick Marchenko, PhD

Industrial Engineer & Automotive Content Specialist

Nick writes in-depth guides on car clubs, engine specs, vehicle ownership, and modifications, combining engineering knowledge with automotive passion.

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