Airbag control unit with part number 4N0959655AD

What does the airbag control unit 4N0959655AD do?

The airbag control unit 4N0959655AD controls the restraint system (SRS) of Audi. It evaluates the signals from the crash sensors, decides in an impact within milliseconds whether airbags and seatbelt pretensioners are triggered, and monitors the system continuously. If it detects a fault, the airbag warning light comes on.

After an accident, the unit stores crash data and locks itself. Only the repair lifts the lock.

Why does the control unit 4N0959655AD fail?

The most common cause is crash data stored after an accident, even if no airbag was deployed; an ordinary diagnostic tool cannot remove it. Other causes are aged electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

The crash data stays stored until it is erased. Airbag24 removes it during the repair.

Electronics age, and solder joints can give way over the years. Moisture and corrosion at plugs disrupt the contact between components.

Voltage spikes, for example from a weak battery or a jump start, can also stress the electronics.

How can you tell that the 4N0959655AD is defective?

The airbag warning light in the instrument cluster stays on or flickers, an error message appears in the instrument cluster, the diagnostic tool finds no connection to the control unit, or the fault memory cannot be cleared. In that case, airbags and seatbelt pretensioners may not deploy in a real crash.

The warning light is the clearest sign. It indicates the fault as soon as the system has detected it, which is exactly what it is for. An error message in the instrument cluster and a fault memory that cannot be cleared are further signs.

If you notice any of these signs, have the system checked promptly so that you know its condition.

Which vehicles is the 4N0959655AD fitted in?

The 4N0959655AD is fitted in these vehicles: Audi RSQ8 4M (2019-2022) and 4M Facelift (from 2024); Audi SQ8 4M (2019-2023) and 4M Facelift (from 2023); Audi Q8 4M Facelift (from 2023) and 4M (2018-2023).

The vehicles at a glance:

• Audi RSQ8 4M (2019-2022)
• Audi RSQ8 4M Facelift (from 2024)
• Audi SQ8 4M (2019-2023)
• Audi SQ8 4M Facelift (from 2023)
• Audi Q8 4M Facelift (from 2023)
• Audi Q8 4M (2018-2023)

Two steps help before removal. Comparing the part number on the label of the removed unit with this page only confirms that it is the correct unit. Also have the fault memory read out. Only this result shows whether the control unit is defective or whether a plug or a cable is the cause.

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 4N0959655AD work?

First have the fault memory read out and enclose the log with the unit. Then disconnect the battery and only afterwards remove the control unit. Next, create a repair order online and send in the well-packed unit. Airbag24 generally needs 3–4 working days for the check, repair and test.

At Airbag24, the unit is first checked on the test bench, and defective components are replaced. The crash data is erased, and a function test completes the work. Your own unit is then returned to you.

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 4N0959655AD get to Airbag24?

You send the unit in as a parcel, or book a UPS collection for an extra charge. After the repair, Airbag24 sends the unit back to you by UPS.

Put the printed repair order into the parcel and pack the unit shock-proof.