Audi Q5 Brake Lights Not Working With The Error On A Dash - How To Fix

By Nick Marchenko, PhD

In the world of automotive DIY, fixing brake light issues on an Audi Q5 can be a daunting task, but with the right guidance, it's entirely achievable. Here's a comprehensive guide that blends wisdom from various enthusiasts with troubleshooting expertise to help you resolve Audi Q5 brake light failures.

Understanding the Problem

The Audi Q5 is a marvel of engineering, but like any vehicle, it's not immune to issues. A common problem some users have encountered involves brake light failures, often indicated by dashboard warnings about malfunctioning rear lights, turn signals, or both. Such issues could arise due to various reasons ranging from fuse problems, control module issues, to broken rear gate sensors.

Diagnosis and Tools Required

Before diving into the repair, it's essential to accurately diagnose the problem. You'll need a few tools at your disposal, including a basic toolkit, a VCDS (VAG-COM Diagnostic System) for scanning the vehicle's diagnostic codes, and potentially a multimeter for checking electrical connections.

Step 1: Scan for Error Codes

Firstly, use a VCDS scanner to read any Diagnostic Trouble Codes (DTCs) related to the lighting system. This step is crucial as it pinpoints the exact nature of the problem, whether it's a specific bulb, wiring issue, or a control module fault.

Step 2: Inspect Fuses and Wiring

Contrary to initial guesses, the tail lights of an Audi Q5 are not controlled by fuses but directly by a lighting control module, known as the J393 module. Despite this, always check for any blown fuses as a preliminary step. Additionally, inspect the wiring, especially around the rear gate hinge, for any signs of wear or damage.

Step 3: Check the Rear Gate Sensor

A broken rear gate sensor can lead to the vehicle thinking the gate is open, thus disabling certain lights. Inspect the sensor and replace it if necessary. References to replacing the tailgate micro switch (part number: 80c959121a) and resetting the condition can be found in specific Technical Service Bulletins (TSBs) provided by Audi.

Troubleshooting Steps

Based on collective advice and technical insights, here are some actionable steps to address common light failure issues:

• Fuse Check: Although not directly related to tail lights, ensure all fuses are intact as a basic troubleshooting step.
• Control Module Investigation: The J393 module, responsible for rear lighting, might need a reset or replacement if diagnostics indicate a fault.
• Wiring and Sensor Inspection: Examine the wiring for any damage, especially around movable parts like the rear gate. Replace any faulty sensors detected during the inspection.
• Bulb Check: Even though it's less likely for LED bulbs to fail simultaneously, inspect them for functionality. Sometimes, the issue might be as simple as a loose connection or a malfunctioning bulb.

Always start with the simpliest. Check the bulbs to ensure that they are in working condition. If some of them show the signs of malfunction - change them to new ones. If you are not sure what bulbs are used on a brake light position of your Audi Q5 - consult the bulb size chart below:

• 2019;
• 2018;
• 2017;
• 2016;
• 2015;
• 2014;
• 2013;
• 2012;
• 2011;
• 2010;
• 2009;

Final Thoughts

While addressing Audi Q5 brake light issues can seem complex, a methodical approach to diagnosing and fixing the problem can save you time and money. Remember, when in doubt, consulting with a professional or referring to your vehicle's manual is always a prudent choice.

For additional resources on maintaining your Audi Q5, consider exploring related topics such as choosing the right tires, understanding common engine issues, and the intricacies of engine swap compatibility. These guides provide valuable insights into keeping your Audi Q5 in top condition.

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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