Airbag control unit with part number A9079000404

What does the airbag control unit A9079000404 do?

The airbag control unit A9079000404 is the central control unit of the SRS restraint system for Mercedes-Benz. It evaluates the signals from the crash sensors and, in an accident, decides within milliseconds whether airbags and seatbelt pretensioners are triggered.

The unit monitors the system continuously and reports faults via the airbag warning light in the instrument cluster. In addition, the manufacturer's number Bosch 0285015025 is printed on the housing.

After an accident it stores crash data and locks itself. The lock is only lifted by the repair.

Why does the control unit A9079000404 fail?

Stored crash data is the most common cause on the A9079000404, even when no airbag has deployed, and a normal diagnostic tool cannot erase it. Ageing components, cold solder joints, moisture on the plugs and voltage spikes can also cause the failure.

The other causes can be summarised as follows:

• ageing electronic components
• cold solder joints
• moisture and corrosion at plug connections
• voltage spikes from a weak battery or a jump start

Airbag24 removes the crash data as part of the repair.

How can you tell that the A9079000404 is defective?

A defect on the A9079000404 shows through the airbag warning light in the instrument cluster, which stays on permanently or intermittently, and through a fault message in the instrument cluster. In addition, the diagnostic tool finds no connection to the control unit.

These signs appear singly or in combination:

• airbag warning light on permanently or intermittently
• fault message in the instrument cluster
• diagnostic tool without a connection to the control unit
• fault memory cannot be cleared

In a crash, airbags and seatbelt pretensioners may then fail to trigger. Please have the condition clarified promptly.

Which vehicles is the A9079000404 fitted in?

The A9079000404 is fitted in these vehicles: Mercedes-Benz Sprinter W907 (from 2018). The part number on the label of the removed unit is used for comparison.

The vehicles in this assignment are shown in the following list:

• Mercedes-Benz Sprinter W907 (from 2018)

The comparison only confirms that you have the correct unit. In addition, have the fault memory read out, because only the record shows whether the control unit is defective or whether a plug or a cable is the cause.

For the same vehicles, we also repair control units with the part numbers 285010033, 285010349, 285011400, 285015024, A 907 900 48 07, A9079000304.

How does the repair of the A9079000404 work?

First comes reading out the fault memory, and the record goes into the parcel. Then you disconnect the battery and only after that remove the control unit A9079000404. Processing at Airbag24 usually takes 3–4 working days.

Afterwards you create the repair order online and pack the unit carefully before you send it.

At the Airbag24 test bench the unit is examined. Defective components are replaced, the crash data is erased and the function is tested. The unit is then 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 A9079000404 get to Airbag24?

You can send the control unit A9079000404 in as a parcel or book a UPS collection for an extra charge. After the repair, the return follows by UPS.

The printed repair order belongs in the parcel, and the unit should be packed shock-resistant.