Audi A4 B6 Comfort Control Module Faults: Common Failures and Repair
The comfort control module (Komfortsteuergerät) on the Audi A4 B6 is one of those components that quietly manages a surprising number of everyday functions — central locking, electric windows, interior lighting, mirror adjustment and the alarm system. When it starts failing, the symptoms can seem completely unrelated to each other, which makes diagnosis genuinely tricky if you don’t know what you’re looking for.
Quick Answer
The Audi A4 B6 comfort control module is a body electronics unit responsible for managing central locking, electric windows, interior lighting and alarm functions. Common failures include water ingress into the module causing short circuits, failed window regulators falsely attributed to the regulator itself, and intermittent central locking faults. A tested used OEM replacement unit, correctly coded to the vehicle, is usually the most cost-effective repair path.
What Does the Comfort Module Actually Do?
On the B6 platform (2001–2005), the comfort module sits in the driver’s door or behind the dashboard depending on the variant. It handles:
- Central locking — including remote key signals
- Electric window control for all four doors
- Interior and courtesy light timing
- Mirror folding and adjustment
- Alarm system arming/disarming
- Rain sensor integration on equipped vehicles
Because so many functions pass through this single module, a partial failure can show up as what seems like several separate problems at once. We’ve had B6s come into the workshop with owners convinced they needed a new window regulator, a new lock actuator and a boot release switch — when the actual culprit was one comfort module with a failed relay inside.
Common Symptoms of Comfort Module Failure
These are the symptoms we see most often on A4 B6 comfort module failures, roughly in order of how frequently they appear:
- Central locking not responding to remote or interior button
- One or more electric windows operating erratically or not at all
- Interior lights staying on permanently or not coming on at all
- Alarm triggering randomly or failing to arm
- Battery drain overnight — the module staying awake on the CAN bus
- One-touch window function working on some doors but not others
- Boot lid release not responding
The battery drain issue is particularly frustrating because owners often replace the battery two or three times before someone scans the car properly and pins it on the comfort module keeping the bus alive. For comparison, see Audi A4 B6 Comfort Control Module Faults: Common Failures and Repair.
Common Error Codes
Scanning with VCDS or a compatible VAG diagnostic tool will usually pull one or more of the following from module address 46 (comfort system):
| Fault Code | Description |
|---|---|
| 01217 | Central locking — open circuit or short to ground |
| 01044 | Control module incorrectly coded / adaptation error |
| 00955 | Interior monitoring — fault in sensor supply |
| 01218 | Central locking — short circuit to positive |
| 00668 | Supply voltage terminal 30 — implausible signal |
| 01226 | Electric window — driver’s side, open circuit |
Code 01044 almost always appears after a module swap — it just means the replacement unit needs to be adapted and coded to the vehicle using VCDS. It’s not a sign of a faulty replacement unit.
Root Causes — Why the B6 Module Fails
Water ingress is the number one cause. The B6 has a known issue with blocked drainage channels in the door card and footwell area. Once moisture gets into the module connector or the module housing itself, corrosion sets in on the PCB traces and relay contacts. You’ll sometimes see the green corrosion clearly when you open the casing.
The second most common cause is simply age and heat cycling. The relay contacts inside the unit wear out over time — especially on the door lock relay which operates every time someone locks or unlocks the car. After 15–20 years and hundreds of thousands of lock cycles, that contact resistance climbs until the relay stops switching reliably.
Occasionally we see damage from a previous amateur repair — someone has poked around in the door and either pulled a connector off under tension or accidentally fed 12V into a signal line.
Common OEM Part Numbers
The following OEM part numbers apply to the Audi A4 B6 comfort control module. Always verify against your vehicle’s build date and options before ordering: A related diagnostic guide is When the Audi A4 B6 Comfort Module Causes Central Locking Problems.
- 8E0 962 258 A — standard comfort module, LHD, without rain sensor
- 8E0 962 258 B — updated revision, same application
- 8E0 962 258 C — with rain sensor integration
- 8E0 962 258 D — Avant / S-line variant
- 8E0 962 258 F — later B6 production, revised relay spec
- 8E0 962 258 H — equivalent used in some B7 carry-over builds
Note that not all of these are interchangeable without recoding. A tested OEM unit sourced from a comparable B6 (same body style, same market) will require the least adaptation work.
Affected Vehicles
The comfort module fault is most commonly reported on:
- Audi A4 B6 Saloon — 2001 to 2004
- Audi A4 B6 Avant — 2001 to 2005
- Audi A4 B6 Cabriolet — 2002 to 2005 (different module part numbers apply)
- Seat Exeo — uses a closely related platform and shared module design
The B7 A4 (2004–2008) carried forward a revised comfort module design, so B6-specific part numbers generally do not apply directly, though some late B6 and early B7 units overlap in spec.
Replacing the Module: What to Know First
Swapping a comfort module is a straightforward job — connector access, remove the unit, plug in the replacement. The critical step people miss is the VCDS coding afterwards. The new unit needs to be told which options are fitted to the car (rain sensor, heated seats, alarm type, market spec). Skip this step and you’ll have partial function at best.
If buying a used OEM unit, make sure you source it from a same-spec vehicle. A comfort module from an RHD car in the UK will not simply plug and play into a LHD European-spec A4. Also check the revision letter — some revisions introduced updated relay specs that are not backward compatible without a software update.
At GiantParts, tested OEM comfort modules are checked for output function before shipping, and each listing includes the part number so you can cross-reference against your own. Worldwide shipping available.
FAQ
Why is my Audi A4 B6 battery draining overnight?
A faulty comfort control module is one of the most common causes of parasitic battery drain on the A4 B6. The module can fail in a state that keeps it awake on the vehicle CAN bus, drawing current continuously. Scan address 46 with VCDS and check for fault codes related to the comfort system before replacing the battery again. For additional context, read Audi A4 B6 Immobilizer and EWS Faults: Diagnosis and Repair Guide.
Can I replace the Audi A4 B6 comfort module myself?
The physical swap is straightforward — unplug the connector and swap the unit. However, the replacement module must be coded and adapted to your car using VCDS or a compatible VAG tool. Without this step, central locking, alarm and window functions will not work correctly. Most independent workshops with VAG diagnostics can do this in under 30 minutes.
What is the Audi A4 B6 comfort module part number?
The most common OEM numbers are 8E0 962 258 A through H, with the exact variant depending on build date, body style and fitted options. Always check the label on your existing unit before ordering a replacement to ensure compatibility, especially regarding rain sensor and alarm spec.
Why are my A4 B6 electric windows not working on one side?
Before replacing the window regulator or motor, scan the comfort module. A failed relay or PCB fault inside the module can cut output to one side only, mimicking a mechanical failure. This is a very common misdiagnosis on the B6. Confirm with VCDS — if code 01226 or similar is logged, the module is the first suspect.
Is a used OEM comfort module safe to fit on my Audi A4 B6?
Yes, provided the unit is tested before sale and the part number matches your vehicle’s spec. A tested used OEM module is typically far more reliable than a cheap aftermarket unit, which often lacks the correct relay specs and can introduce new faults. Source from a supplier that checks output function and confirms compatibility — and always have it coded after fitting.
Find tested OEM electronic parts and modules at:
https://giantparts.eu/
