Audi, Porsche & VW Side Assist Failure (2011-2018): Your Guide to the Blind Spot Module

Symptoms of a Failing Side Assist Module

When the right-side blind spot module fails, you will typically notice several distinct warnings. The system often deactivates completely as a safety measure.

• "Audi Side Assist: System Fault" or "LCA Fault" Message: This is the most common symptom. A warning will appear on your instrument cluster display, indicating the system is inoperative.
• "The selected system is currently not available": When you try to activate or adjust Side Assist in the MMI (Multi Media Interface), this message may appear.
• Mirror Indicator Lights Don't Work: The warning lights in your side mirrors will not light up when a car is in your blind spot. They may also fail to perform the initial check-flash when you start the car.
• Inability to Activate the System: Pressing the Side Assist button on the driver's door or in the MMI does nothing, and the system cannot be turned on.
• Incorrect Warnings: In some cases, a faulty module might cause the warning light to illuminate for the wrong side of the car. For example, a car on the driver's side triggers the passenger mirror light. This often happens if an incompatible part is installed.

Common OBD-II and Diagnostic Fault Codes

To properly diagnose this issue, a VAG-specific scanner (like VCDS or OBDeleven) is needed, as generic OBD-II readers may not communicate with the Side Assist module (Address 3C). Common fault codes include:

• 16365 / B200FF9: Control Module - Electrical Error / Defective. This points to an internal failure of the module itself.
• C12030: No communication with lane change assist control unit. This indicates a wiring, fuse, or complete module failure.
• C1115F5: Lane change assistance control module 2 Restricted view. This can be caused by a software issue, dirt, or module misalignment.
• Control module not coded / Data record invalid: These codes often appear after a replacement attempt if the module has not been properly programmed to the vehicle.

Known Issues, TSBs, and Common Causes of Failure

These modules are prone to failure for a few common reasons, primarily related to their exposed location.

1. Water Intrusion and Corrosion

The modules are mounted low in the corners of the rear bumper, making them highly susceptible to water, road salt, and grime kicked up by the tires. Over time, moisture can penetrate the module's casing or its electrical connector, causing corrosion and short circuits. This is the most frequent cause of failure reported by owners in forums.

2. Physical Damage or Misalignment

Even a minor bumper impact, like a parking lot tap, can crack the module's housing or break its mounting bracket. If the module is knocked out of its precise alignment, it will fail its self-calibration check and shut down, triggering a fault message.

3. Software and Intermittent Faults (TSBs)

Audi and Porsche have issued Technical Service Bulletins (TSBs) for certain software-related issues:

• TSB 2033943 (Audi): Addresses a condition where the system shows a "Sensors blocked" message during heavy stop-and-go traffic or on long, empty roads. This is considered normal software behavior designed to prevent false readings, not a part failure. The system should return to normal 🎬 See how the 'sensors blocked' warning appears on Porsche models. after about ten minutes of regular driving or an ignition cycle.
• TSB 2039096/1 (Audi): Relates to false warnings on some A5 models where the mirror light activates without a vehicle present. A software update (SVM code 3CA013) is available to fix this.
• Porsche TSB 2108.1: Notes an intermittent "faulty control unit" error (B200FF9) on some Cayenne models. The bulletin advises that the fault is temporary and often self-heals, and that parts replacement is ineffective.

Replacement: Not a Simple DIY Job

Replacing this module involves much more than just swapping the part. The process requires special tools and software access, making it a job for a dealership or a well-equipped independent specialist.

1. Bumper Removal: The rear bumper cover must be removed to access the modules.
2. Component Protection (CP): This is the biggest hurdle. Component Protection is an anti-theft system used by Audi, VW, and Porsche. When a new or used module is installed, it will be 'locked' by the vehicle's gateway. Its functions will be disabled until the protection is removed. This can only be done online by connecting the vehicle to the manufacturer's servers using dealer-level diagnostic tools (like ODIS with a GeKo account).
🎬 Learn more about how Component Protection removal works.
3. Calibration: After installation and CP removal, the radar module must be calibrated. This process aims the sensor precisely and requires a special radar calibration rig. Driving without proper calibration can make the system unreliable or inoperative.

Because of Component Protection and the need for calibration, a simple DIY swap will not work. The part will not function until it is programmed and calibrated by a professional.

Buying a Used Body Control Module

Buying a used OEM module is a great way to save a significant amount of money, as new units are very expensive. However, you must be extremely careful to buy the correct part and understand the additional costs involved.

Key Compatibility Checks:

• Match the Part Number Exactly: Do not deviate from the OEM part number on your original module. While several numbers are listed for this platform, you must match yours.
• Master vs. Slave Warning: These vehicles use a 'master' and a 'slave' module. The right (passenger) side module this article covers is the slave. A critical compatibility trap exists between models. For the Audi Q5, VW Touareg, and Porsche Cayenne, the slave module (ending in ...568) is on the right side. However, for the Audi A4, A5, S4, and S5, the configuration is inverted, and the slave module is on the left. Installing a module from the wrong model will cause the system to work in reverse.
• Check Software Version: Some owners report that matching the software version number printed on the module's label, in addition to the main part number, can help avoid compatibility issues.
• Inspect for Damage: Check photos for any cracks in the plastic housing or corrosion on the connector pins. Avoid any parts showing signs of water damage.

Cost Breakdown for Replacement

Prices can vary based on location and the specific shop. These are estimates to help you understand the potential costs.

Frequently Asked Questions (FAQ)