Airbag control unit with part number 4N0959655AJ

What does the airbag control unit 4N0959655AJ do?

The airbag control unit 4N0959655AJ coordinates the restraint system (SRS) of Audi. It processes the signals from the crash sensors, determines in a collision which airbags and seatbelt pretensioners are triggered, and checks the system continuously. The unit shows faults via the airbag warning light.

The unit keeps working without interruption. Evaluation must succeed in an emergency in a split second.

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

Why does the control unit 4N0959655AJ fail?

The most common cause on the 4N0959655AJ is stored crash data after an accident, even if no airbag has triggered. A standard diagnostic tool cannot erase it. Other causes are also possible.

Crash data also arises in an impact in which no airbag triggers. A diagnostic tool of the usual kind does not make it disappear.

Further causes include these points:

• aged electronic components
• cold solder joints
• moisture and corrosion at plug connections
• voltage spikes, for example with a weak battery or jump-starting

How can you tell that the 4N0959655AJ is defective?

A defect on the 4N0959655AJ shows itself through an airbag warning light in the instrument cluster that is on permanently or intermittently, an error message in the instrument cluster, a diagnostic tool without connection, or a fault memory that cannot be cleared. In an emergency, airbags and seatbelt pretensioners may then possibly fail to deploy.

The warning light is the first indication that the system has detected a fault. Have the fault memory read out promptly.

A diagnostic tool that makes no connection also points to the fault. Only a detailed read-out shows whether the control unit or the cables to it are affected.

Which vehicles is the 4N0959655AJ fitted in?

The unit 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). If your model fits, only the part number 4N0959655AJ decides.

The models for this number are shown in the list:

• 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 checks make sense before removal. The part number on the label either matches this page or it does not, and that only establishes the identity of the unit. The fault memory, by contrast, shows whether the unit itself is defective or whether a plug or 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 4N0959655AJ work?

First have the fault memory of the 4N0959655AJ read out and attach the log. Then disconnect the battery and remove the control unit. Next, create the repair order online; processing at Airbag24 usually takes 3–4 working days.

Send the unit in well packed. Airbag24 examines it on the test bench, replaces defective components, erases stored crash data and carries out a function test. You get your own unit back afterwards.

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 4N0959655AJ get to Airbag24?

You send the control unit 4N0959655AJ either as a parcel or choose a UPS collection for an extra charge. The return after the repair follows via UPS.

Enclose the printed repair order with the parcel, and the packaging must be shock-proof.