Airbag control unit with part number A2139008928

What does the airbag control unit A2139008928 do?

The airbag control unit A2139008928 controls the restraint system (SRS) in the Mercedes-Benz. It evaluates the crash sensors, determines within milliseconds in a crash which airbags and seatbelt pretensioners to trigger, and monitors the system continuously.

A detected fault is shown by the airbag warning light in the instrument cluster, so that the driver notices it.

After an accident it stores crash data and locks itself.

Why does the control unit A2139008928 fail?

Most often the cause is found in stored crash data, even if no airbag has deployed. Ageing and moisture effects in general, as well as cold solder joints and voltage spikes, are also possible.

Crash data cannot be erased with normal diagnostic tools. It therefore needs to be considered separately during fault-finding.

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

How can you tell that the A2139008928 is defective?

The airbag warning light in the instrument cluster indicates the defect. You should also watch for an error message, a missing connection to the diagnostic tool and a fault memory that cannot be cleared.

• light stays on permanently or keeps coming on
• error message in the instrument cluster
• diagnostic tool cannot establish a connection to the control unit
• fault memory cannot be cleared

While the fault persists, the airbags and seatbelt pretensioners may not trigger in an emergency. Treat the light as a warning signal.

Which vehicles is the A2139008928 fitted in?

The A2139008928 is fitted in these vehicles: Mercedes-Benz E-Class S213 Estate (2016-2023) and W213 Saloon (2016-2023).

The assignment to the models is shown in this list:

• Mercedes-Benz E-Class S213 Estate (2016-2023)
• Mercedes-Benz E-Class W213 Saloon (2016-2023)

Comparing the part number on the label of the removed unit with this page ensures that it is the correct unit. Have the fault memory read out beforehand, because only the log shows whether the control unit is defective or whether plugs and cables are the cause.

For the same vehicles, we also repair control units with the part numbers A213 900 46 25, A213 900 88 22, A213 900 88 28, A2139007105, A2139010104.

How does the repair of the A2139008928 work?

First have the fault memory read out and enclose the log. Then disconnect the battery and remove the control unit. Next, create a repair order online and send in the well-packed unit.

Airbag24 tests the control unit on the test bench, replaces defective components, erases the stored crash data and carries out a function test. Afterwards your own unit is returned to you. Checking, repairing and testing at Airbag24 usually takes 3–4 working days.

The order of the first steps is mandatory, as it protects safety during removal and transport. 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 A2139008928 get to Airbag24?

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

Make sure the printed repair order is in the parcel and that the unit is packed shockproof.