Airbag control unit with part number 8H0 959 655 B

What is the function of the airbag control unit 8H0 959 655 B?

The airbag control unit with part number 8H0 959 655 B is the central control unit for the occupant protection system in the Audi A4 B6 (series 8E). As an original Audi component (OEM) manufactured by Bosch, it processes data from crash sensors and, in the event of a collision, controls the deployment of airbags and seatbelt pretensioners.

This component is primarily installed in the Audi A4 of the B6 generation, produced between 2000 and 2004, including convertible models. It serves as the brain of the entire airbag system, ensuring the proper functioning of all safety-related restraint systems.

Technically, it is a device manufactured by Bosch, known under various Bosch-specific numbers such as 0285001652 or 0285001703. These numbers are often directly interchangeable and refer to the same hardware and software platform. Repairing these units is a common practice, as new parts from the manufacturer are often expensive or no longer available.

Why does the control unit 8H0 959 655 B fail?

Defects in the control unit 8H0 959 655 B typically arise due to aging electronic components, electrical disturbances in the vehicle’s electrical system, or, following a crash, stored crash data. Internal hardware failures on the circuit board, software issues, or communication malfunctions frequently lead to failure and the illumination of the airbag warning light.

The most common reason for necessary repair is the storage of crash data after a collision. This data locks the control unit and often cannot be cleared using standard diagnostic tools. Similarly, age-related failures of components such as microcontrollers, capacitors, or internal memory chips can cause malfunctions.

Other typical fault patterns include problems within the fault memory itself, such as software errors, sporadic communication interruptions with the diagnostic tool, or incorrect coding that impairs functionality. In many cases, related part numbers like 8H0 959 655 D are also affected, as they share a similar platform.

An important note from workshop experience: Before removing the control unit, the fault memory should be read out and the error codes documented. This information significantly speeds up diagnosis and subsequent repair.

How do you recognize a defect in the 8H0 959 655 B?

A defect in the airbag control unit 8H0 959 655 B mainly manifests as a permanently or intermittently illuminated airbag warning light in the instrument cluster. Another clear indication is that the control unit can no longer be accessed via the diagnostic interface or reports communication errors.

The primary and unmistakable symptom is the active airbag warning light. It signals a fault in the safety system and results in failure during the main inspection (HU). The light may either remain on continuously after starting the engine or flash irregularly during driving.

Another frequent sign is a communication problem during vehicle diagnostics. When a workshop attempts to read the fault memory, it may be unable to establish a connection with the airbag control unit. The unit fails to respond to requests from the diagnostic tool, indicating a serious internal defect.

In which vehicles is the control unit 8H0 959 655 B installed?

The airbag control unit 8H0 959 655 B was specifically developed for the Audi A4 of the B6 generation. At Airbag24, we repair this unit and its compatible counterparts for the corresponding models, restoring full functionality of the safety system and avoiding the costly purchase of a new unit.

At Airbag24, the control unit with part number 8H0 959 655 B is serviced for the following model:

Audi A4 B6 (series 8E), model years 2000–2004, including convertible variants.

How does the repair of the 8H0 959 655 B proceed at Airbag24?

At Airbag24, upon receipt, the control unit undergoes a professional repair process. This includes an initial inspection, analysis of reported faults, elimination of hardware and software defects, and a final functional test. We provide 2 years' statutory liability for defects on all repairs performed.

After the removed control unit arrives at Airbag24, our technicians conduct a thorough analysis to identify the exact cause of the fault. Based on this diagnosis, defective electronic components—such as circuit boards, capacitors, or microcontrollers—are professionally replaced.

A key step is processing the internal memory. Stored crash data is completely erased, and if necessary, the device’s software is updated to address known issues. Finally, the control unit is tested on a specialized test bench to simulate and verify the correct operation of all systems.