Airbag control unit with part number A4479001118

What does the airbag control unit A4479001118 do?

The airbag control unit A4479001118 is the central control unit of the restraint system (SRS) for Mercedes-Benz. It evaluates the signals from the crash sensors, decides in an accident within milliseconds whether to trigger airbags and seatbelt pretensioners, and monitors the system continuously.

The manufacturer's part number Bosch 0285020147 is additionally stamped on the housing. The airbag warning light in the instrument cluster indicates faults in the system.

After an accident the control unit stores crash data and locks itself. This fact alone determines how the unit responds to readout and testing afterwards, and nothing more belongs in the description of the function.

Why does the control unit A4479001118 fail?

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

Crash data arises regardless of whether the airbags have fired. A normal diagnostic tool cannot remove it, and so fault finding can be laborious.

Electronic components age, and over time the contact at solder joints can be lost. Moisture and corrosion at plug connections disturb signal transmission.

Voltage spikes arise, for example, from a weak battery or jump-starting. They can damage the electronics.

How can you tell that the A4479001118 is defective?

The airbag warning light in the instrument cluster lights up permanently or intermittently, and a message appears in the display. In addition, the diagnostic tool gets no connection to the control unit, and the fault memory remains.

Typical signs are:

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

In an emergency, airbags and seatbelt pretensioners may not be able to deploy if the defect is present. Please therefore take the indication seriously.

Which vehicles is the A4479001118 fitted in?

The A4479001118 is fitted in these vehicles: Mercedes-Benz Vito W447 (from 2014); Mercedes-Benz V-Class W447 (from 2014).

The vehicles from the stored data are listed here:

• Mercedes-Benz Vito W447 (from 2014)
• Mercedes-Benz V-Class W447 (from 2014)

Compare the part number on the label of the removed unit with this page. This only ensures that it is the right unit. Have the fault memory read out beforehand, because only the result shows whether the control unit itself is the cause or a plug or cable.

For the same vehicles, we also repair control units with the part numbers 4479006309, A 447 900 10 00, A4479000900, A4479010300.

How does the repair of the A4479001118 work?

First have the fault memory read out and enclose the log. Then disconnect the battery and remove the control unit. Then create a repair order online and pack the unit well. Airbag24 checks, repairs and tests it as a rule within 3–4 working days.

The order is fixed for safety reasons. The control unit may only be removed after the battery has been disconnected.

At Airbag24 the unit goes onto the test bench. Defective components are replaced, stored crash data is erased and a function test is carried out. Afterwards your own unit 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 A4479001118 get to Airbag24?

You send the unit in a parcel or book a UPS collection for an extra charge. After the repair, UPS brings the unit back to you.

The printed repair order goes into the parcel. Pack the control unit shockproof so that it survives shipping undamaged.