Airbag control unit with part number 4N0959655AK

What does the airbag control unit 4N0959655AK do?

The airbag control unit 4N0959655AK controls the restraint system (SRS) of Audi. In an impact it decides within milliseconds which airbags and seatbelt pretensioners to trigger, and it continuously checks the components involved. After an accident it stores crash data and locks itself.

The signals from the crash sensors converge in the control unit and are evaluated there. If the system detects a fault, it reports it via the airbag warning light.

In everyday use the unit works in the background. It remains in operation at all times, even if you do not notice anything.

Why does the control unit 4N0959655AK fail?

The most common cause is crash data that remains in the memory after an accident, even if no airbag has triggered. A normal diagnostic tool cannot remove it. Other causes include aged components, cold solder joints, moisture and corrosion, and voltage spikes, for example from a weak battery or jump-starting.

As long as nobody deliberately removes the data, it stays in the unit's memory.

Electronics age over the years, and contacts corrode gradually. Voltage spikes in the on-board power supply also stress sensitive components.

How can you tell that the 4N0959655AK is defective?

Typical signs are an airbag warning light that lights up permanently or intermittently, error messages in the instrument cluster, no connection to the diagnostic tool and a fault memory that cannot be cleared.

In detail, a fault shows itself as follows:

• The airbag warning light in the instrument cluster lights up permanently or intermittently.
• An error message appears in the instrument cluster.
• The diagnostic tool gets no connection to the control unit.
• The fault memory cannot be cleared.

As long as the fault persists, airbags and seatbelt pretensioners may not trigger in an emergency. The warning light is intended to draw your attention to this condition.

Which vehicles is the 4N0959655AK fitted in?

The 4N0959655AK is found in these vehicles: Audi RS6 C8 (2019-2025); Audi RSQ8 4M (2019-2022) and 4M Facelift (from 2024); Audi RS7 C8 4K Facelift (2023-2025) and C8 4K (2019-2023); Audi SQ8 4M (2019-2023) and 4M Facelift (from 2023); Audi Q8 4M Facelift (from 2023) and 4M (2018-2023).

The individual vehicles are listed directly below.

• Audi RS6 C8 (2019-2025)
• Audi RSQ8 4M (2019-2022)
• Audi RSQ8 4M Facelift (from 2024)
• Audi RS7 C8 4K Facelift (2023-2025)
• Audi RS7 C8 4K (2019-2023)
• Audi SQ8 4M (2019-2023)
• Audi SQ8 4M Facelift (from 2023)
• Audi Q8 4M Facelift (from 2023)
• Audi Q8 4M (2018-2023)

Two separate checks belong to this. Comparing the label with this page only confirms that you have the right unit in front of you. Reading out the fault memory beforehand shows, by contrast, whether the control unit itself is defective or whether a plug or cable is responsible.

For the same vehicles, we also repair control units with the part numbers 4M0959655, 4M0959655AL, 4M0959655E, 4N0 959 655AE, 4N0959655A, 4N0959655AC.

How does the repair of the 4N0959655AK work?

First have the fault memory read out and attach the log. Then disconnect the battery and only then remove the control unit. Finally, create a repair order online and send in the unit, carefully packed.

At Airbag24 the unit is first checked on the test bench. Defective components are repaired, and stored crash data is deleted. A function test concludes the work, after which your own unit is returned to you.

Processing at Airbag24 usually takes 3–4 working days.

Our repairs come with 2 years' statutory liability for defects.

The repaired control unit comes back with all vehicle data and is ready for use as soon as it is refitted — no coding or programming is required.

How does the control unit 4N0959655AK get to Airbag24?

You send the control unit 4N0959655AK in as a parcel yourself, or you book a UPS collection for an extra charge. The return after the repair is likewise made by UPS.

Place the printed repair order in the parcel and pad the control unit shockproof.