Airbag control unit with part number 4H0959655B

What is the function of the airbag control unit 4H0959655B?

The airbag control unit with part number 4H0959655B is the central control module for the passive safety system in various high-end Audi models. It processes signals from crash sensors and is responsible for precisely and promptly deploying airbags and seatbelt pretensioners in the event of a collision.

This component continuously monitors all connected sensors, airbag modules, and seatbelt pretensioners for proper functionality. If a fault occurs in the system or an accident is detected, the unit stores relevant information and activates the airbag warning light on the instrument cluster to alert the driver.

Why does the control unit 4H0959655B fail?

The most common causes of failure for the control unit 4H0959655B are stored crash data following an accident that locks the system, as well as internal electronic malfunctions. These often arise due to age-related wear of components or general electrical disturbances in the vehicle’s wiring harness.

A primary cause is the storage of crash data. After an accident, the control unit locks itself for safety reasons and must either be replaced or professionally reset. As long as this data remains, the airbag system cannot function properly.

In addition, hardware defects on the circuit board can lead to failure. Faulty electronic components such as microcontrollers or capacitors may disrupt internal data processing or even result in a complete communication breakdown. Such defects are typical consequences of aging and thermal stress over time.

How do you recognize a defect in the 4H0959655B?

A defective airbag control unit 4H0959655B primarily manifests through two clear symptoms: the airbag warning light on the dashboard remains constantly illuminated, and there is no communication with the control unit during diagnostics. These signs indicate a serious internal malfunction.

The most obvious symptom is the persistently lit airbag warning light. It does not turn off after starting the vehicle, signaling that the passive safety system is not operational. The fault memory often contains entries such as “control unit defective” or “internal error.”

Another critical symptom is a complete loss of communication. When a workshop attempts to access the control unit via the OBD port, the connection fails. The unit does not respond to diagnostic requests, making precise fault analysis impossible without removal.

In which vehicles is the 4H0959655B installed?

The airbag control unit 4H0959655B is installed in various high-end Audi models. It is mainly used in the A6, A7, and A8 series produced between 2010 and 2021, including their respective facelift versions.

At Airbag24, we repair the control unit 4H0959655B for the following Audi models:

Audi A6: C7 4G (2010–2014) and C7 4G Facelift (2014–2018)

Audi A7: C7 4G (2010–2014) and C7 4G Facelift (2014–2018)

Audi A8: D4 4H (2010–2013), D4 4H Facelift (2013–2017), D5 4N (2017–2021), and D5 4N Facelift (from 2021 onward)

What are the advantages of repair compared to replacement?

Repairing the original control unit offers significant benefits: substantial cost savings compared to a new part, preservation of the vehicle’s original coding, and an environmentally friendly solution. Additionally, the repaired unit is immediately ready for installation (plug-and-play).

From a financial perspective, repair is the most economical option. It is considerably cheaper than purchasing a new unit, which often costs several hundred euros, or a used replacement with an uncertain history.

A key technical advantage is maintaining the original coding. Since the vehicle’s original control unit is refurbished, there is no need for time-consuming reprogramming or relearning by the vehicle. After repair, the unit can simply be reinstalled and will function right away.

Lastly, repair represents a sustainable alternative, promoting the reuse of electronic components and helping reduce electronic waste.

How does the repair of the 4H0959655B work at Airbag24?

The repair process at Airbag24 is designed for maximum efficiency and safety. After submitting the removed control unit, our technicians perform a thorough diagnosis, fix the defect at the component level, erase any stored crash data, and conclude with a comprehensive functional test.

Once the control unit has been removed at a specialized workshop, please send it to us. Upon arrival at Airbag24, the unit undergoes an initial inspection to verify the reported fault and identify any additional potential issues.

Subsequently, professional repair is carried out. Depending on the fault pattern, defective components such as microcontrollers or capacitors on the circuit board are replaced, and stored crash data is erased in compliance with legal requirements. Each step is performed according to the highest quality standards.

Before being returned, every repaired control unit undergoes a final test on our test benches to ensure the flawless operation of all system components. We provide 2 years' statutory liability for defects on every repair.