Airbag control unit with part number 5WK44111

What is the function of the airbag control unit 5WK44111?

The Bosch airbag control unit 5WK44111 is the central control module for the occupant protection system in the Audi A4 B8 (8K). It analyzes data from acceleration and seatbelt force sensors to precisely deploy airbags and pretensioners in the event of a crash. Additionally, it logs system-relevant faults and stores crash data after a collision.

As the brain of the passive safety system, this control unit continuously monitors and evaluates signals from crash sensors distributed throughout the vehicle. Within milliseconds, it determines whether and how extensively restraint systems—such as front, side, and head airbags—as well as seatbelt pretensioners should be activated.

Following a crash, relevant information—known as crash data—is securely stored in the unit’s internal memory. This feature locks the control unit against further use and ensures that the airbag warning light remains illuminated until professional repair is performed.

Why does the control unit 5WK44111 fail?

The most common cause of failure for the 5WK44111 control unit is stored crash data that cannot be erased after an accident. Other typical defects include internal electronic malfunctions (error code B200049), power supply issues (U101100), and communication problems (U015100) with the vehicle. Software and coding errors may also occur.

A key reason for failure is the storage of crash data. This deliberate lockout by the manufacturer after deployment prevents reuse without proper inspection and is not considered a defect in the traditional sense; however, it requires professional reprogramming to unlock the device.

Hardware-related failures often manifest as internal electronic faults, indicated by error code B200049. Possible causes include defective components on the circuit board or issues with the internal power supply (error U101100). Communication errors (U015100) likewise point to an internal fault that disrupts communication with other vehicle components.

This control unit and its associated fault patterns can also be found under other part numbers within the same platform. Compatible variants for the Audi A4 B8 include, for example, 5WK43749, 5WK44482, 8K0959655J, 8K0959655P, and 8K0959655L.

How do you recognize a defect in the 5WK44111?

A defect in the 5WK44111 control unit primarily shows up as a permanently illuminated or intermittently flashing airbag warning light on the instrument cluster. Often, the control unit can no longer be accessed via the OBD interface, complicating diagnosis. Typical entries in the fault memory include U101100, B200049, or U015100.

The clearest symptom is the active airbag warning light, signaling a problem with the restraint system and resulting in failure during the main vehicle inspection. In this state, the vehicle offers little or no occupant protection.

Another clear indication is when the control unit becomes unreachable by diagnostic equipment. The workshop is then unable to establish a connection to read out the fault memory or perform diagnostics. This complete loss of communication strongly suggests an internal fault within the control unit.

When reading the fault memory (if communication is possible), specific error codes provide valuable clues. Codes such as B200049 (internal electronic fault), U101100 (undervoltage), or U015100 (communication error) directly point to a problem within the control unit itself.

In which vehicles is the 5WK44111 installed?

The Bosch airbag control unit with part number 5WK44111 is specifically designed for the Audi A4 of the B8 series (8K). At Airbag24, we repair this control unit for both the pre-facelift generation from 2007 to 2011 and the facelift models produced from 2011 to 2015.

Our repair expertise at Airbag24 covers the entire model generation of the Audi A4 B8. Specifically, these variants are included:

Audi A4 B8 8K (model years 2007–2011)

Audi A4 B8 8K Facelift (model years 2011–2015)

How is the 5WK44111 control unit professionally repaired?

Professional repair of the 5WK44111 at Airbag24 begins with an initial inspection to verify the reported fault. This is followed by technical restoration, which—depending on the nature of the defect—involves reprogramming the processor and erasing crash data. After a final functional test, you receive a fully operational control unit backed by 2 years' statutory liability for defects.

Before removing the unit from the vehicle, a thorough diagnosis is recommended. Reading and documenting the fault memory ensures that the defect can be clearly attributed to the control unit itself and not to peripheral components such as wiring or sensors.

After being sent to Airbag24, the control unit undergoes a comprehensive analysis. If crash data is available, it is completely erased through reprogramming of the memory. In cases of hardware defects, faulty electronic components on the circuit board are identified and replaced.

Subsequently, the refurbished control unit undergoes a final test on our test benches to ensure flawless functionality across all systems. The unit is returned in plug-and-play condition, allowing it to be reinstalled in the vehicle without additional coding. We provide 2 years' statutory liability for defects on every repair.

Is repairing the 5WK44111 worthwhile?

Repairing the 5WK44111 offers significant cost savings compared to purchasing a new part, whose price often amounts to several times that of a refurbished unit. A repaired control unit is a plug-and-play solution, as the original vehicle coding is preserved, eliminating the need for time-consuming reprogramming at the workshop. Additionally, our 2 years’ statutory liability for defects guarantees the quality of the refurbishment.

Another key advantage over a used replacement part is certainty. With a used unit, the history is often unknown, and latent defects may already be present. Repairing the original component ensures that it has been thoroughly inspected and is fully functional.

Retaining the original control unit also avoids compatibility issues that can arise from differing software or hardware versions in aftermarket parts. Thus, repair is not only the most economical but also the technically safest option.