How to Fix an Acura TL Brake Light Failure

By Nick Marchenko, PhD

Having a brake light failure in your Acura TL can be a perplexing issue, but with some patience and a systematic approach, it's a problem you can often solve yourself. The guide below combines insights from various experiences and provides a comprehensive approach to troubleshooting and resolving brake light issues in an Acura TL.

Initial Inspection

• Check Fuses: Begin with the basics. Inspect the STOP (20A) fuse under the hood and the Fuse 9 (7.5A) in the driver's under-dash. Use a multimeter to check for continuity. Even if a fuse looks intact, it might still be faulty.
• Inspect the Brake Light Bulbs: Make sure all brake light bulbs, including the center high-mount stop lamp, are functioning. Replace any that are burnt out. 

You can view the brake light bulb size for your Acura TL here:

• 2013
• 2012
• 2011
• 2010
• 2009
• 2008
• 2007
• 2006
• 2005

Electrical Checks

• Brake Pedal Position Switch: This switch is crucial for the operation of brake lights. Confirm that the WHT/YEL wire has 12V and the WHT/BLK wire has 12V when the brake pedal is pressed. If there's no power, the switch might be faulty.
• Shift Lock and Interlock Switch: The shift lock system is often linked to the brake light circuit. If the brake lights don't work, the car might not shift out of park. Check the switch and its connections.
• Wiring and Connectors: Follow the wiring from the Brake Pedal Position Switch to the rear Brake Light Failure Sensor. Look for any open circuits, damaged wires, or melted connectors. Pay special attention to Connector O behind the under-dash fuse box, as it is a common point of failure.

Advanced Troubleshooting

• Continuity Testing: Use a multimeter to check for continuity at every splice and connector in the brake light circuit. This includes connections to the anti-lock brake system, the underdash fuse/relay box, the high mount brake light, the brake light failure sensor, and the trailer lighting connector in the trunk.
• PCM and ABS Connections: Although less common, issues can occur in the wiring related to the Powertrain Control Module (PCM) and the anti-lock braking system (ABS). Consult a wiring diagram for specifics.

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Repairs and Solutions

• Replacing the Brake Light Switch: If the brake light switch is faulty, replace it. This is a common issue and can often be the root cause of brake light failure.
• Repairing or Replacing Connectors: If you find a damaged connector, like Connector O, you can either splice the wires outside the connector or replace the connector entirely. For a more secure and long-lasting repair, consider soldering the wires and using heat-shrink tubing.
• Addressing Grounding Issues: Ensure all ground connections, especially those in the trunk or under the spare tire, are secure and not disturbed. This is crucial if you've recently had work done in these areas.
• Reporting Major Issues: If you encounter a significant issue like a melted connector or a widespread wiring problem, consider reporting it to automotive safety authorities. This could indicate a broader safety issue.

Additional Tips

• Use a Car Manual: Refer to your car's manual for specific diagrams and wiring layouts. This can greatly aid in identifying and tracing circuits.
• Don’t Overlook Simple Solutions: Sometimes the issue can be as simple as a loose bulb or a slightly off-positioned switch. Double-check these before diving into complex troubleshooting.
• Safety First: Always work with the car turned off and the keys removed from the ignition when handling electrical components.

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By systematically checking each component and carefully repairing or replacing faulty parts, you can effectively address brake light issues in your Acura TL. Remember, electrical work can be intricate, so if you're not confident in your abilities, consult a professional.

See also:

• How To Change Headlight Bulb On 2007 Acura TL Without Removing Bumper

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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