Airbag control unit with part number 4E0 959 655 H

What is the function of the airbag control unit 4E0 959 655 H?

The airbag control unit with part number 4E0 959 655 H is the central control unit for the entire occupant protection system in Audi A8 and S8 models of the D3 generation. It continuously monitors the sensors and is responsible for precisely and reliably deploying the airbags and seatbelt pretensioners in the event of a crash.

As a product from Bosch, this unit serves as the brain of the passive safety system. It collects and processes real-time data from various acceleration and pressure sensors strategically distributed throughout the vehicle.

Based on these sensor signals, the control unit determines within milliseconds whether the severity of a collision warrants triggering the safety components. These include front, side, and head airbags, as well as pyrotechnic seatbelt pretensioners.

A properly functioning control unit is critical for occupant safety, as a malfunction can result in complete failure of the entire airbag system.

Why does the control unit 4E0 959 655 H fail?

The most common cause of failure for the control unit 4E0 959 655 H is the storage of crash data after an accident. This data locks the device out of further operation as a safety precaution. Additional failures may arise from electronic component defects on the circuit board or communication issues within the internal memory.

The primary reason requiring repair is the irreversible storage of crash data following an airbag deployment. After such an event, the control unit self‑locks to prevent reuse in a potentially damaged vehicle. A professional reset is then essential.

Independently of accidents, internal electronic components can also degrade and fail over time. This may lead to a complete breakdown in communication with the vehicle’s diagnostic system or other control units.

For technical identification, it’s important to note that this Bosch control unit is also listed under the Audi equivalent number 4E0910655D. During diagnosis or when searching for replacement parts, this cross-reference is crucial to avoid compatibility issues.

How do you recognize a defect in the 4E0 959 655 H?

A defect in the control unit 4E0 959 655 H almost always manifests as a permanently illuminated airbag warning light on the instrument cluster. Often, the control unit can no longer be read by a diagnostic tool, indicating an internal communication error or total failure.

The most obvious and frequent symptom is the persistently lit airbag warning light in the cockpit. This signal should never be ignored, as it indicates that the entire passive safety system may be disabled.

In the workshop, a clear defect becomes apparent when communication with the control unit via the OBD‑II interface cannot be established. Diagnostic tools receive no response, making it impossible to retrieve fault codes.

Consequently, this results in complete failure of the airbag system. In the event of an actual crash, critical safety components like airbags and seatbelt pretensioners would not deploy, posing a significant safety risk.

In which vehicles is the control unit 4E0 959 655 H installed?

The airbag control unit 4E0 959 655 H is specifically designed for Audi’s luxury sedans. It is used in the Audi A8 D3 series as well as in the sporty S8 D3 model. At Airbag24, we offer expert repairs for all variants of these vehicles.

At Airbag24, we repair the control unit with part number 4E0 959 655 H for the following specific models and production periods:

Audi A8: D3 4E (model years 2002–2005) and the D3 4E facelift (model years 2005–2010).

Audi S8: D3 (model years 2006–2008) and the D3 facelift (model years 2008–2010).

Thus, the control unit covers both pre‑facelift and post‑facelift versions of the D3 platform, ensuring broad compatibility within this vehicle generation.

How does the repair of the 4E0 959 655 H proceed at Airbag24?

After removal and shipment of the control unit to Airbag24, the device undergoes an initial inspection. The core of the repair is professionally erasing the stored crash data. Subsequently, full functionality is verified on a test bench before the unit is returned with 2 years’ statutory liability for defects.

The repair process at Airbag24 is designed for maximum safety and reliability. Upon receipt of your package, the control unit is clearly identified and subjected to a comprehensive incoming analysis.

The key technical step involves accessing the control unit’s internal memory and professionally, thoroughly erasing the stored crash data. This restores the unit to its pre-accident operational condition.

If, beyond the crash data, diagnostics reveal additional electronic defects on the circuit board, our technicians will perform the necessary component-level repairs.

Before returning the control unit, it undergoes a final functional test on a specialized test bench. This ensures that communication and all safety‑critical functions operate flawlessly. Every repair is backed by 2 years' statutory liability for defects.