Airbag control unit with part number 4H0959655D

What does the airbag control unit 4H0959655D do?

The airbag control unit 4H0959655D is the central unit of the restraint system (SRS) for Audi. It processes the signals from the crash sensors and, in an accident, decides within milliseconds which airbags and seatbelt pretensioners are triggered. At the same time it monitors the system and indicates faults via the airbag warning light.

The manufacturer number Bosch 0285010921 is additionally printed on the housing.

In operation the unit continuously checks whether all components deliver signals.

After an accident it records crash data and locks itself.

Why does the control unit 4H0959655D fail?

Stored crash data is the most common cause in the 4H0959655D, even if no airbag fired in the accident. A normal diagnostic tool cannot erase it, but Airbag24 removes it during the repair. Other causes are ageing, moisture at plug connectors and voltage spikes.

Electronic components age, and solder joints can cause contact problems.

Moisture and corrosion at plug connectors disrupt signal transmission, and the contact becomes unreliable.

Voltage spikes, for example from a weak battery or after a jump start, additionally stress the electronics.

How can you tell that the 4H0959655D is defective?

The airbag warning light in the instrument cluster lights permanently or intermittently if a fault is present on the 4H0959655D. Accompanying this, a fault message may appear in the instrument cluster, the diagnostic tool finds no connection to the control unit, or the fault memory cannot be erased.

The light indicates the defect as soon as the system detects it. If the fault memory persists, the fault must be investigated more closely.

As long as the fault is present, the airbags and seatbelt pretensioners may not be able to fire in an emergency. A prompt check is therefore advisable.

Which vehicles is the 4H0959655D fitted in?

The airbag control unit 4H0959655D is fitted in these vehicles: Audi A6 C7 4G Facelift (2014-2018) and C7 4G (2010-2014).

Here is the assignment in detail:

• Audi A6 C7 4G Facelift (2014-2018)
• Audi A6 C7 4G (2010-2014)

Compare the part number on the label of the device with this page so that you have the right unit. That is only an assignment. Whether the control unit is defective or a plug or cable is the cause is shown only when the fault memory has been read out, which you should arrange beforehand.

For the same vehicles, we also repair control units with the part numbers 285010856, 4G0959655A, 4G0959655B, 4H0 959 655 C, 4H0959655B, 4H0959655H.

How does the repair of the 4H0959655D work?

First have the fault memory read out and attach the log to the unit. Then disconnect the battery and only then remove the control unit. Create a repair order online, and send the well-packed unit in. At Airbag24, checking, repairing and testing usually take 3–4 working days.

In the lab, Airbag24 first tests the unit on the test bench. Then defective components are replaced, stored crash data is erased and a function test is carried out.

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. Your unit comes back to you afterwards.

How does the control unit 4H0959655D get to Airbag24?

The control unit 4H0959655D goes to Airbag24 either as a parcel or via a UPS collection booked for an extra charge. The return after the repair is made by UPS. The printed repair order is included in the parcel.

Pack the unit shockproof so that it survives transport unharmed.