Airbag control unit with part number 5WK44637

What is the function of Airbag Control Unit 5WK44637?

The airbag control unit with part number 5WK44637 is the central control module for the occupant restraint system (SRS) in vehicles such as the Audi A4 8K and A5 8TA. It processes data from crash sensors in real time to ensure that, in the event of a collision, the appropriate airbags and seatbelt pretensioners are deployed precisely and at the right moment.

As the “brain” of the safety system, this control unit—often associated with OE part number 8K0 959 655 N—performs several critical tasks. It continuously receives and analyzes signals from acceleration and crash sensors distributed throughout the vehicle. Based on this data, it evaluates the type and severity of an impact—whether frontal, side, or rear-end.

On the basis of this analysis, the 5WK44637 control unit determines which restraint systems need to be activated. It controls the deployment of individual airbags and seatbelt pretensioners in a precisely defined sequence and intensity, ensuring optimal protection for occupants.

In addition, the device performs continuous self-diagnosis of the entire airbag system, monitoring all connected components for proper functionality. If a fault is detected, it is stored in the fault memory, and the airbag warning light on the instrument panel illuminates to alert the driver. Via the CAN bus, it also communicates with other control units in the vehicle.

Why does Airbag Control Unit 5WK44637 fail?

The most common causes of failure for the 5WK44637 control unit include internal electronic faults on the circuit board, such as defective microcontrollers or memory chips, as well as a permanently stored crash data record following an accident. External factors like moisture or age-related solder joint cracks can also lead to complete failure.

A primary cause lies within the hardware itself. Internal components—including the microcontroller, memory ICs (EEPROM/Flash), or power supply—can deteriorate over time. Open circuits or cold solder joints resulting from thermal stress and vibration over years are also typical reasons for the “control unit defective” error.

A very frequent reason for service is a stored crash data record. After a collision in which airbags or seatbelt pretensioners have been deployed, the control unit locks itself internally. This lock (crash data) cannot be cleared using conventional diagnostic tools, preventing further operation of the airbag system—even if all deployed components have been replaced.

External influences, such as corrosion caused by water ingress into the vehicle interior, can likewise damage sensitive electronics. This leads to short circuits or destroys components and connectors, often resulting in a complete loss of communication with the control unit.

How do you recognize a defect in Control Unit 5WK44637?

A defect in the 5WK44637 airbag control unit almost always manifests as a persistently illuminated airbag warning light on the dashboard. Other clear indicators include entries in the fault memory such as “control unit defective” or “internal error,” as well as complete inability to communicate with the control unit during diagnostics.

The most obvious symptom is the constantly lit airbag warning light. It does not extinguish after starting the vehicle, signaling a serious malfunction in the safety system. Such a vehicle would fail to pass a mandatory technical inspection.

In the workshop, the defect often becomes apparent when communication with the control unit via a diagnostic tool (e.g., VCDS, ODIS) is no longer possible. The control unit fails to respond to requests, making further troubleshooting of sensors or airbags impossible.

When fault codes are read, specific entries like “control unit defective” or “error in control unit” directly point to an internal hardware fault. Additionally, non-erasable crash data following an accident is a clear indication that the control unit requires repair.

In which vehicles is Control Unit 5WK44637 installed?

The airbag control unit with manufacturer’s part number 5WK44637 and its corresponding OE number 8K0 959 655 N is primarily found in various models of the Audi A4 and A5 series from the late 2000s and early 2010s. Repairing this component ensures continued functionality in these specific vehicles.

At Airbag24, we repair part number 5WK44637 for the following models:

Audi A4 (series 8K / B8, including Avant)

Audi A5 Sportback (series 8TA, pre-facelift 2007–2011 and facelift 2011–2016)

How is Control Unit 5WK44637 professionally repaired?

Professional repair of the 5WK44637 control unit involves precise diagnosis of the internal fault, expert deletion of crash data, replacement of defective electronic components such as memory ICs or microcontrollers, and a final functional test on a test bench to guarantee full operability.

After submission to Airbag24, the repair process follows a proven procedure. First, an incoming inspection is performed, during which the fault memory is read out and the exact defect—whether an internal hardware failure, a communication issue, or stored crash data—is analyzed.

Next, the housing is carefully opened to inspect the circuit board. Our technicians examine the board microscopically for defective solder joints, corrosion, or damaged components. Defective parts such as voltage regulators, CAN transceivers, or memory chips are replaced with new, high-quality components.

A key step is handling the device’s software. Stored crash data is erased from the EEPROM/Flash memory, while the vehicle-specific coding remains fully intact. This ensures that, after installation, the control unit functions without requiring time-consuming reprogramming.

Finally, the repaired control unit is simulated on a specialized test bench. Here, all functions are tested under real-world conditions. Only when communication operates flawlessly and no internal errors remain is the unit approved for return shipment. We provide 2 years' statutory liability for defects on every repair.