Airbag control unit with part number 4N0959655AG

What does the airbag control unit 4N0959655AG do?

The airbag control unit 4N0959655AG controls the restraint system (SRS) of Audi. It uses the crash sensors to detect whether an impact has occurred and decides within milliseconds which airbags and seatbelt pretensioners to fire. It also checks the system continuously and reports faults via the airbag warning light.

After an accident, the unit stores crash data and locks itself. The lock is only lifted by the repair.

Why does the control unit 4N0959655AG fail?

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

The data stays in memory until it is deliberately erased. Airbag24 takes care of this during the repair.

Electronics age, and components can fail over time. Solder joints on the circuit board can give way over the years.

Moisture and corrosion at connectors disrupt contact. Voltage spikes, for example from a weak battery or a jump start, can also damage the electronics.

How can you tell that the 4N0959655AG is defective?

A fault shows up as an airbag warning light that stays on or flickers, as an error message in the display, as a diagnostic tool that cannot connect to the control unit, or as a fault memory that cannot be cleared. In that case, airbags and seatbelt pretensioners may not deploy in a real crash.

The typical signs at a glance:

• The airbag warning light stays on or flickers.
• An airbag system message appears in the instrument cluster.
• A diagnostic tool gets no connection to the control unit.
• The fault memory remains even after an attempt to clear it.

If the light is on, have the system checked. It is the most reliable sign that the system has detected a fault.

Which vehicles is the 4N0959655AG fitted in?

The 4N0959655AG 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 list of vehicles follows here:

• 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 come before removal. Compare the part number on the label of the removed unit with this page. This only confirms that it is the correct unit. Also have the fault memory read out. Only this log shows whether the control 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 4N0959655AG work?

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

Airbag24 checks the unit on the test bench and replaces defective components. The stored crash data is erased, followed by a function test. You then receive your own unit back.

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 4N0959655AG 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. Pack the unit shock-proof so it survives shipping undamaged.