Airbag control unit with part number A2229000009

What does the airbag control unit A2229000009 do?

The airbag control unit A2229000009 controls the restraint systems (SRS) of Mercedes-Benz. It processes the signals from the crash sensors and decides in an accident, within fractions of a second, which airbags and seatbelt pretensioners trigger. After an accident it stores crash data and locks itself.

The evaluation runs throughout operation. The unit checks its sensors and triggering circuits constantly, even when nothing seems wrong in everyday use.

It shows faults via the airbag warning light in the instrument cluster. You may therefore only notice that it is working through this light, not through any other function.

Why does the control unit A2229000009 fail?

Stored crash data after an accident is the most common cause, even if no airbag has deployed, and a normal diagnostic tool cannot delete it. Other causes are ageing electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes.

Stored crash data remains in the unit until it is read out or deleted. A diagnostic tool from a workshop cannot remove it, which is why such a fault does not disappear with a simple reset.

The other causes concern the electronics themselves. Ageing components and cold solder joints interrupt contacts, while moisture and corrosion at plug connections disturb the signal paths.

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

How can you tell that the A2229000009 is defective?

You cannot directly recognise stored crash data. The fault becomes visible through the airbag warning light, which lights up permanently or intermittently, through a fault message in the instrument cluster, through a diagnostic tool without connection, and through a fault memory that cannot be cleared.

The airbag warning light in the instrument cluster is the most important sign. It shows a fault that the unit has itself detected, which means that airbags and seatbelt pretensioners could possibly not deploy in an emergency.

• Airbag warning light in the instrument cluster stays on permanently
• Airbag warning light comes on only intermittently
• Fault message in the instrument cluster
• Diagnostic tool cannot find the control unit
• Fault memory cannot be cleared

Which vehicles is the A2229000009 fitted in?

The A2229000009 is fitted in these vehicles: Mercedes-Benz S-Class W222 Saloon (2013-2020).

The following overview shows the vehicles that are stored for this part number.

• Mercedes-Benz S-Class W222 Saloon (2013-2020)

Check the part number on the label of the removed unit against this page. This only tells you that it is the correct unit. Have the fault memory read out before you change anything on the unit, because only then will it become clear whether the control unit is defective or whether a plug or cable is responsible for the fault.

For the same vehicles, we also repair control units with the part numbers A2229000303, A2229009908, A2229012601, A2229013503, A2229024709.

How does the repair of the A2229000009 work?

Read out, enclose the log, disconnect the battery, then remove: this order applies for safety reasons. Then create a repair order online and pack the unit well before sending it in. Processing at Airbag24 usually takes 3–4 working days.

Airbag24 checks the unit on the test bench and replaces defective components. Stored crash data is deleted, then a functional test is carried out. Afterwards your own unit is returned 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 A2229000009 get to Airbag24?

You send the unit in as a parcel or book UPS collection for an extra charge. After the repair, Airbag24 sends it back to you by UPS.

Enclose the printed repair order in the parcel and pack the unit shock-resistant.