Airbag control unit with part number 4M0959655AB

What does the airbag control unit 4M0959655AB do?

The airbag control unit 4M0959655AB controls the restraint system (SRS) for Audi. It evaluates the crash sensors, determines within milliseconds in an accident which airbags and seatbelt pretensioners trigger, and stores crash data after an accident. Afterwards it locks itself.

It monitors the system continuously and shows faults via the airbag warning light. In addition, the manufacturer's number Bosch 0285015531 is printed on the housing.

Triggering is reliable only when signals, electronics and wiring work together and without faults.

Why does the control unit 4M0959655AB fail?

Stored crash data on the 4M0959655AB is the most common cause, even if no airbag has fired; a normal diagnostic tool cannot erase it. Further causes are ageing electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

Crash data remains in the memory after an accident. During repair at Airbag24 it is erased.

The other causes act over a longer period or arise from external influences such as wetness or a weak battery. Which cause is present only the test shows.

How can you tell that the 4M0959655AB is defective?

A defect on the 4M0959655AB shows first on the airbag warning light in the instrument cluster. Then the airbags and seatbelt pretensioners may not be able to deploy in a crash.

Typical signs are:

• Airbag warning light stays on permanently or intermittently
• Fault message in the instrument cluster
• No connection between diagnostic tool and control unit
• Fault memory cannot be cleared

If you notice any of these, have the system checked promptly. The warning light reports the fault as soon as the system detects it.

Whether the control unit, a connector or a cable is affected is decided by the test.

Which vehicles is the 4M0959655AB fitted in?

The 4M0959655AB 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 list shows the vehicles recorded for this part number.

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

You make the label comparison on the removed unit: if the number matches this page, you have the right unit. The cause, however, is established only by the fault memory, which you have read out before removal. Only it shows whether the control unit is defective or whether a connector 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 4M0959655AB work?

Have the fault memory of the 4M0959655AB read out and attach the log, then disconnect the battery and remove the control unit. Afterwards create the repair order online and send the unit in; processing at Airbag24 usually takes 3–4 working days.

Airbag24 tests the unit on the test bench, rectifies defects on components, erases stored crash data and carries out a function test. The unit then goes back to you.

The 3–4 working days refer only to this testing, repairing and checking.

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 4M0959655AB get to Airbag24?

You send the control unit 4M0959655AB in as a parcel. Alternatively, you book a UPS collection for an extra charge, and Airbag24 returns the repaired unit by UPS.

The printed repair order goes into the parcel; the unit is packed shock-proof.