How to Fix Porsche Cayenne Brake Light Fail: A DIY Guide

Step 1: Fuse Inspection

1. Locate the Fuse Box: Begin by inspecting the fuses related to the brake light system. The fuse box is typically located on the driver’s side.
2. Check and Replace if Necessary: Identify fuse #38 (10 amp) and any other fuses related to the brake light circuit. If a fuse is blown, replace it with a new one of the same rating.

Step 2: Bulb and Assembly Check

1. Access the Brake Light Assembly: Open the rear hatch to access the brake light assemblies on both sides of the vehicle.
2. Inspect and Replace Bulbs: Remove the brake light bulbs and inspect them for any signs of damage or wear. Replace both bulbs simultaneously to ensure consistent resistance and performance across the system.
3. Check for LED Functionality: If your Cayenne is equipped with LED brake lights, a failure in one of the LEDs might affect the entire assembly. Consider replacing the entire light assembly if individual LEDs are not functioning.

If you are planning a bulb replacement, but not sure what bulb size is used on a brake light position of your Porsche Cayenne - consult the chart below:

• 2015;
• 2014;
• 2013;
• 2012;
• 2011;
• 2010;
• 2009;
• 2008;
• 2006;
• 2005;
• 2004;
• 2003;

Step 3: Battery and Electrical System

1. Battery Inspection: A low battery can sometimes cause issues with the electrical systems, including the brake lights. If the vehicle has been experiencing electrical oddities, test the battery and replace it if necessary.
2. Reset the Bulb Control Module: Disconnect the battery ground for about 10 minutes to reset the bulb control module. This can sometimes resolve the issue without needing further repairs.

Step 4: Ground and Wiring Check

1. Inspect Ground Connections: A common issue that might cause brake light failures is a poor ground connection. Check the ground connections near the brake light assembly and clean or tighten as necessary.
2. Wiring Inspection: Look for any signs of damaged or frayed wiring that could affect the brake lights. Pay particular attention to the wiring harness leading to the brake light assembly.

Step 5: Module and Controller Inspection

1. Rear Comfort Module: The rear comfort module controls various functions, including the brake lights. If the above steps haven't resolved the issue, consider inspecting this module for faults or connection issues.
2. Rear Control Module Replacement: In some cases, the rear control module might be the culprit. This part is usually located in the rear hatch area. Replacement might require professional assistance due to the complexity of accessing and installing a new module.