Airbag control unit with part number 4N0959655

What does the airbag control unit 4N0959655 do?

The airbag control unit 4N0959655 forms the central control unit of the restraint system (SRS) of Audi. It processes the messages from the crash sensors, determines within milliseconds in an accident which airbags and seatbelt pretensioners are triggered, and checks the entire system without interruption. It displays detected faults via the airbag warning light.

In everyday use the unit runs all the time and evaluates sensor data without you noticing anything. In an emergency the decision has to be made in fractions of a second, which is why the electronics are designed for fast and reliable evaluation.

If an accident occurs, the unit stores crash data and locks itself.

Why does the control unit 4N0959655 fail?

The most common cause is crash data stored after an accident, even if no airbag has been triggered, and a normal diagnostic tool cannot erase it. Other possible causes include aged components, cold solder joints, moisture and corrosion on plugs, and voltage spikes.

The crash data is the main focus, but the electronics also age: components lose reliability over time, solder joints can go cold, and moisture attacks plug connections.

A weak battery or a jump start also introduces voltage spikes into the vehicle electrical system, which can stress the unit. Which cause is present in an individual case is shown only by examining the control unit.

How can you tell that the 4N0959655 is defective?

A defect in control unit 4N0959655 shows up as the airbag warning light in the instrument cluster, which stays on permanently or intermittently. Added to this may be fault messages, no connection to the diagnostic tool, and a fault memory that cannot be cleared.

Typical signs are:

• Airbag warning light in the instrument cluster stays on permanently or intermittently
• Fault message in the instrument cluster
• Diagnostic tool finds no connection to the control unit
• Fault memory remains

In an emergency, the airbags and seatbelt pretensioners may then fail to deploy. A timely check of the system is therefore advisable.

Which vehicles is the 4N0959655 fitted in?

The control unit 4N0959655 for Audi 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). These details refer to the part number itself.

The vehicles in detail:

• 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)

Compare the part number on the label of the removed unit with this page. This only confirms that it is the right unit. Also have the fault memory read out before removal, because only the result shows whether the control unit itself is the cause or whether a plug or cable is affected.

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 4N0959655 work?

Reading out the fault memory comes first, along with the enclosed log; only afterwards do you disconnect the battery and remove control unit 4N0959655. Then create a repair order online and pack the unit well. Processing at Airbag24 usually takes 3–4 working days.

At Airbag24 the unit is examined on the test bench, defective components are repaired, and a function test follows. Crash data is erased by Airbag24 during this repair. Afterwards your own unit comes back 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 4N0959655 get to Airbag24?

You send control unit 4N0959655 as a parcel to Airbag24, or you book a UPS collection for an extra charge. After the repair, Airbag24 brings the unit back by UPS.

The printed repair order belongs in the parcel. A shock-proof carton protects the control unit on its way to us.