Airbag control unit with part number 4M0959655BB

What does the airbag control unit 4M0959655BB do?

The airbag control unit 4M0959655BB is the central control unit of the restraint system for Audi. It evaluates the signals from the crash sensors, decides within milliseconds in a crash whether airbags and seatbelt pretensioners are triggered, and monitors the system constantly.

The unit reports faults via the airbag warning light in the instrument cluster. The monitoring covers all connected components.

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

Why does the control unit 4M0959655BB fail?

Stored crash data after an accident is the most common cause in the control unit 4M0959655BB, even if no airbag was triggered. Aged electronic components, cold solder joints, moisture and corrosion on plug connectors, and voltage spikes are also possible causes. With this control unit, the crash data often cannot be erased; if you want it erased, contact Airbag24 briefly before sending the unit in, and Airbag24 will check the part number.

Crash data therefore remains the starting point of every check, even when it cannot always be removed.

Aged components and cold solder joints can show up under changing conditions. Moisture and corrosion mainly attack plug connectors, and voltage spikes arise, for example, with a weak battery or jump-starting.

How can you tell that the 4M0959655BB is defective?

The airbag warning light in the instrument cluster lights up constantly or intermittently, and a fault message appears in the instrument cluster. The diagnostic tool cannot connect to the control unit 4M0959655BB, and the fault memory cannot be cleared.

In an emergency, the airbags and seatbelt pretensioners may then fail to trigger. Have the system checked promptly while the warning light is on.

The cause only becomes clear when the fault memory is read out.

Which vehicles is the 4M0959655BB fitted in?

The airbag control unit 4M0959655BB is fitted in these vehicles: Audi Q7 4M (2015-2019) and 4M Facelift (2019-2024); Audi SQ7 4M (2016-2019) and 4M Facelift (from 2019).

The following vehicles are assigned to this unit:

• Audi Q7 4M (2015-2019)
• Audi Q7 4M Facelift (2019-2024)
• Audi SQ7 4M (2016-2019)
• Audi SQ7 4M Facelift (from 2019)

Before sending it in, two checks help. Compare the part number on the label of the removed unit with this page, which only confirms that it is the right unit. Also have the fault memory read out, because only that shows whether the control unit is defective or a plug or cable is the cause.

For the same vehicles, we also repair control units with the part numbers 4KE959655B, 4KE959655J, 4KE959655L, 4M0 959 655 AF, 4M0 959 655 G, 4M0 959 655 K.

How does the repair of the 4M0959655BB work?

First, have the fault memory read out and enclose the log. Then disconnect the battery and only then remove the airbag control unit 4M0959655BB. Next, create a repair order online and send in the well-packed unit.

Airbag24 checks the unit on the test bench, replaces defective components if necessary and carries out a function test. Your own unit then goes back to you. Processing at Airbag24 usually takes 3–4 working days and covers only checking, repairing and testing.

If you want the crash data erased, contact Airbag24 briefly before sending the unit in.

The sequence up to removal serves safety and is binding.

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 4M0959655BB get to Airbag24?

You send the control unit 4M0959655BB in as a parcel, or book a UPS collection for an extra charge. After the repair, Airbag24 returns the unit by UPS.

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