Airbag control unit with part number 4E0 959 655 L

What does the airbag control unit 4E0 959 655 L do?

The airbag control unit 4E0 959 655 L is the central control unit of the restraint system (SRS) in Audi. It processes the data from the crash sensors and decides in a collision within milliseconds which airbags and seatbelt pretensioners are triggered.

During operation the unit monitors the entire system constantly. If it detects a deviation, it stores the fault and reports it via the airbag warning light.

After an accident the control unit secures crash data and then locks itself. The lock is lifted only by the repair.

Why does the control unit 4E0 959 655 L fail?

The most common cause is crash data stored after an accident, even if no airbag was triggered. An ordinary diagnostic tool cannot erase it. Ageing electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes also play a role.

The crash data stays in the memory even if the vehicle continues to drive without any noticeable problem. Without targeted reading out, you learn nothing about it.

The other causes act over time. Solder joints become brittle, moisture attacks plugs, and voltage spikes from the vehicle electrical system stress the electronics.

How can you tell that the 4E0 959 655 L is defective?

The airbag warning light in the instrument cluster stays on permanently or intermittently, a fault message appears, the diagnostic tool gets no connection to the control unit, and the fault memory cannot be cleared. In that case the airbags and seatbelt pretensioners may not be triggered in an emergency.

The warning light shows the defect and is therefore the most important warning sign. Never ignore it; have the fault checked promptly.

A missing connection to the diagnostic tool is also among the indications. In this case only a thorough examination of the electronics and the wiring helps.

Which vehicles is the 4E0 959 655 L fitted in?

Whether a vehicle has this unit fitted depends on its equipment and year of manufacture. The 4E0 959 655 L is fitted in these vehicles: Audi S8 D3 (2006-2008) and D3 Facelift (2008-2010); Audi A8 D3 4E (2002-2005) and D3 4E Facelift (2005-2010).

Airbag24 lists these vehicles for this part number:

• Audi S8 D3 (2006-2008)
• Audi S8 D3 Facelift (2008-2010)
• Audi A8 D3 4E (2002-2005)
• Audi A8 D3 4E Facelift (2005-2010)

Comparing the part number on the label of the removed unit with this page ensures that you have the correct unit. In addition, have the fault memory read out beforehand, because only the result 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 0285001672, 0285001705, 285001512, 285001705, 4E0 959 655 H, 4E0910655.

How does the repair of the 4E0 959 655 L work?

First have the fault memory read out and enclose the log. Then disconnect the battery and only afterwards remove the control unit. Create the repair order online and send the unit in well packed. Testing, repairing and checking at Airbag24 usually take 3–4 working days.

Airbag24 checks the unit on the test bench, replaces defective components and deletes the stored crash data. A function test follows, after which your own unit goes back to you.

Keep to the order of removal, as it is there for your safety. Only once the battery is disconnected can the airbag system be accessed without risk.

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 4E0 959 655 L get to Airbag24?

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

The printed repair order belongs in the parcel. The unit should be packed shock-proof so that it survives shipping undamaged.