Audi A4, A6, S4, S6 Comfort Control Module Failure: The Definitive Water Damage Guide (1999-2008)
This guide covers the common water-related failure of the Comfort Control Module in 1999-2004 Audi A6, 2002-2005 Audi A4, 2002-2003 Audi S6, 2004-2008 Audi S4, and other related models, causing electrical chaos with windows, locks, and lights.
- The primary cause of failure is water damage from clogged plenum or sunroof drains, which floods the module's location under the front carpet.
- A replacement module MUST be coded to the vehicle using a tool like VCDS, but a dealer visit is not required and it is not tied to the immobilizer.
- When buying a used module, you must match the part number exactly, including the final letter suffix, to ensure key fob compatibility.
- Do not install a replacement module without first finding and fixing the source of the water leak.
The #1 Cause of Failure: Water Damage
The single most common reason for Comfort Control Module (CCM) failure in this generation of Audi vehicles is water intrusion. Audi engineers placed the module in a plastic box located on the floor of the car, under the carpet in the front footwell — typically on the driver's side for the Audi A4/S4 and the passenger's side for the Audi A6/S6/allroad. This low-lying position makes it extremely vulnerable to moisture that collects in the cabin.
This water damage is almost always caused by two preventable issues:
- Clogged Plenum Drains: The plenum area, located under the battery and brake booster at the base of the windshield, has drain holes designed to let rainwater escape. When these drains get clogged with leaves, dirt, and other debris, the plenum tray fills up like a bathtub, and water spills over into the cabin through the firewall, soaking the carpet and flooding the CCM.
- Clogged Sunroof Drains: Vehicles equipped with a sunroof have four drain tubes, one at each corner, that run down the pillars of the car. If these tubes become clogged, water backs up and overflows, often leaking into the headliner and down into the footwells.
Warning: Simply replacing a failed CCM without addressing the source of the water leak will result in the new module failing as well. Before installing a replacement part, you must clear all plenum and sunroof drains to prevent future damage.
Symptoms of a Failing Comfort Control Module
When the CCM begins to fail, usually due to corrosion on its internal circuit board from moisture, it can cause a wide range of bizarre electrical problems. Symptoms often appear or worsen after a heavy rainstorm.
🎬 Watch: Top 7 symptoms of a bad control module- Erratic Windows and Locks: Power windows may stop working, operate intermittently, or even open and close on their own. The central locking system may fail to respond to the key fob or door switch.
- Interior Lights Malfunction: Interior dome or map lights may stay on, flicker, or not turn on when a door is opened.
- Alarm System Issues: The factory alarm may trigger randomly for no reason, or you may be unable to arm or disarm it.
- Key Fob Inoperable: The remote lock, unlock, and trunk release functions on the key fob may stop working entirely.
- Battery Drain: A faulty, water-damaged module can create a parasitic draw that drains the vehicle's battery when parked.
- No Communication with Scan Tools: When trying to diagnose the issue, a mechanic or DIYer may find they cannot communicate with the Central Convenience module (Address 46) using a diagnostic tool like VCDS.
Vehicle Fitment and Compatibility
This guide specifically covers the Comfort Control Module shared by the following North American market vehicles:
- 1999-2004 Audi A6 (C5 platform)
- 2002-2005 Audi A4 (B6 platform)
- 2002-2003 Audi S6 (C5 platform)
- 2004-2008 Audi S4 (B6 & B7 platforms)
- 2001-2005 Audi allroad (C5 platform)
- 2003-2004 Audi RS6 (C5 platform)
- 2007-2008 Audi RS4 (B7 platform)
Compatibility Warning: The 2004-2006 Volkswagen Phaeton is sometimes incorrectly listed as sharing this part. This is false. The Phaeton is built on a different platform and uses a completely different Body Control Module (e.g., part number 3D0937049H) that is not interchangeable.
Programming and Installation Requirements
Replacing the Comfort Control Module is not a simple plug-and-play repair. The replacement module must be coded to match the specific options and features of your vehicle.
Is Dealer Programming Required?
For this generation of vehicles, a trip to the dealer is usually not necessary. An experienced independent mechanic or a DIYer with the proper tools can program a used CCM. The key requirements are:
- Module Coding: The replacement module needs to be coded with a diagnostic tool like VCDS (VAG-COM). This involves connecting to the car, accessing the Central Convenience module (Address 46), and inputting a specific code that tells the module which features the car has (e.g., number of power windows, alarm type, etc.). It is highly recommended to read and save the coding from your old module before it fails completely, if possible.
- Key Fob Matching: After the module is installed and coded, the key fobs must be re-synchronized to the new module so the remote functions will work. This procedure can also be done with VCDS or through a manual process involving one key in the ignition and another in the driver's door lock.
Pro Tip: Unlike newer Audis, the CCM in these models is NOT linked to the vehicle's immobilizer system. Swapping the module will not prevent the car from starting, even before it has been properly coded. This makes using a recycled OEM part a safe and cost-effective option.
Buying a Used Body Control Module
A used OEM Comfort Control Module is an excellent alternative to an expensive new part. However, because water damage is so common, careful inspection is critical.
- Match the Part Number EXACTLY: There are many different CCM part numbers. You must match the full number, including the final letter suffix (e.g., 4B0 962 258 J). The suffix letter is especially important as it often indicates the radio frequency (e.g., 433MHz) for the key fobs. Using a module with a different suffix may result in the remotes not working.
- Inspect for Corrosion: Carefully examine the pins in the electrical connectors on the module. Look for any signs of green or white crusty corrosion, which indicates past moisture exposure. Do not buy a module that shows any signs of water damage.
- Open the Case if Possible: Ask the seller if you can unclip the plastic housing to inspect the internal circuit board. Any discoloration, rust, or chalky residue on the board is a major red flag.
- Buy From a Reputable Source: Purchase from a recycled parts seller that offers a warranty. This protects you in case the module is dead on arrival or fails shortly after installation. 🎬 Learn how to choose and replace your replacement module
Cost Breakdown
The cost to replace a Comfort Control Module can vary significantly based on the parts source and labor rates.
| Part/Service | Estimated Cost | Notes |
|---|---|---|
| Used OEM Module | $50 - $150 | Price depends on part number and availability. This is the most common repair route. |
| New OEM Module | $450 - $600+ | Purchased from an Audi dealership. Prices for electronic modules can be very high. |
| Shop Labor | $150 - $300 | Includes removing interior trim, replacing the module, and coding it to the vehicle. Labor is typically 1.5-2.5 hours. |
| Total Estimated Cost (Used Part) | $200 - $450 | This represents the most likely total cost for a successful repair. |
Frequently Asked Questions (FAQ)
Do I have to go to the Audi dealer to program a replacement CCM?
No, for these specific models, an independent shop with Audi-specific diagnostic tools like VCDS or Autel can code the module and match the keys. An advanced DIYer can also perform the programming.
Will my car start if I install a used CCM?
Yes. The Comfort Control Module on these C5 and B6/B7 platform vehicles is not part of the engine immobilizer system. The car will start and run with a replacement module installed, even before it is coded, though many interior features will not work correctly until programming is complete.
Where is the Comfort Control Module located?
It is under the carpet in the front of the cabin. In the Audi A4/S4/RS4, it is typically under the driver's side carpet. In the larger Audi A6/S6/RS6/allroad, it is usually found under the passenger's side carpet. You will need to remove the door sill trim and other plastic panels to lift the carpet for access.
🎬 See this walkthrough on how to remove the moduleHow can I prevent my replacement CCM from getting wet?
Prevention is key. At least once a year, you must clean the plenum drains under the battery and the sunroof drains. Pouring a small amount of water into the sunroof channels and ensuring it drains out onto the ground behind the front wheels and in front of the rear wheels is a good test. Keeping the plenum area free of leaves and debris is the most important step.
Helpful Videos
Technical Specifications
OEM Part Numbers: 4B0907491 4B0962258J 4B0962258C 8H0959433M Note: Many other part numbers and revisions exist.
Controls central locking, power windows, key fob frequency, alarm, and interior lighting.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Audi A6:
- Audi A4:
- Audi S6:
- Audi S4:
- Audi allroad:
- Audi RS6:
- Volkswagen Phaeton:
- Audi RS4:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- The #1 Cause of Failure: Water Damage
- Symptoms of a Failing Comfort Control Module
- Vehicle Fitment and Compatibility
- Programming and Installation Requirements
- Is Dealer Programming Required?
- Buying a Used Body Control Module
- Cost Breakdown
- Frequently Asked Questions (FAQ)
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