Airbag control unit with part number 8A0959655D

What does the airbag control unit 8A0959655D do?

The airbag control unit 8A0959655D controls the triggering in the restraint system (SRS) of Audi. It receives the signals from the crash sensors, determines in a collision which airbags and seatbelt pretensioners are triggered, and monitors the system during operation. Faults are displayed via the airbag warning light.

The evaluation takes only milliseconds and runs throughout operation. The unit also re-evaluates the measured values constantly.

The manufacturer number Bosch 0285001039 is also printed on the housing. After a crash, the unit stores crash data and locks itself; only the repair lifts the lock.

Why does the control unit 8A0959655D fail?

Stored crash data is the most common cause on the 8A0959655D, even when no airbag has triggered in the accident. A standard diagnostic tool cannot remove it. Aged components, cold solder joints, moisture and corrosion, as well as voltage spikes, are also considered causes.

Crash data arises even from an impact in which no airbag fires. It lies in the memory of the unit and stays there until the repair takes place.

The other causes build up slowly. Electronics age, solder joints give way, moisture attacks the plug connections, and voltage spikes occur, for example with a weak battery or jump-starting.

How can you tell that the 8A0959655D is defective?

Typical signs of the 8A0959655D are an airbag warning light in the instrument cluster that is on permanently or intermittently, an error message on the display, and a diagnostic tool that makes no connection to the control unit. In addition, the fault memory cannot be cleared, and airbags and seatbelt pretensioners may possibly fail to deploy in an emergency.

These signs are clear enough to act on:

• warning light in the instrument cluster, permanently or intermittently
• error message in the instrument cluster
• diagnostic tool without contact to the control unit
• fault memory that cannot be cleared

A displayed defect does not stay hidden; the warning light points to it. Have the fault memory read out soon.

Which vehicles is the 8A0959655D fitted in?

The part number determines which vehicles come into question. The airbag control unit 8A0959655D is fitted in these vehicles: Audi A6 C4 4A (1994-1997); Audi A4 B5 8D (1994-1999) and B5 8D Facelift (1999-2001).

The following vehicles are listed for this number:

• Audi A6 C4 4A (1994-1997)
• Audi A4 B5 8D (1994-1999)
• Audi A4 B5 8D Facelift (1999-2001)

Before removal, compare the part number on the label with this page; this only confirms that you have the right unit. Have the fault memory read out in advance as well, because only the log shows whether the control unit is defective or whether a plug or cable is the cause.

For the same vehicles, we also repair control units with the part numbers 028 500 1036, 028 500 1038, 028 500 1086, 028 500 1106, 4A0 959 655, 8A0 959 655 A.

How does the repair of the 8A0959655D work?

At the start, the fault memory is read out, and you attach the log to the unit. Only then do you disconnect the battery and remove the 8A0959655D. Online you create the repair order. Processing at Airbag24 usually takes 3–4 working days.

Pack the unit well and send it to us. We examine it on the test bench, replace defective components, erase stored crash data and carry out a function test. Your own unit then goes 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 8A0959655D get to Airbag24?

You send the control unit 8A0959655D as a parcel, or you book a UPS collection for an extra charge. After the repair, the return is made via UPS.

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