Airbag control unit with part number A2139009022

What does the airbag control unit A2139009022 do?

As the central element, the airbag control unit A2139009022 controls the restraint system (SRS) in Mercedes-Benz vehicles. It continuously checks the crash sensors and, in the event of an accident, triggers airbags and seatbelt pretensioners within milliseconds. Detected faults are indicated via the airbag warning light.

To do this, the unit constantly processes the measured values of the connected sensors and compares them with target values.

After an accident, it records crash data and locks itself. Airbag24 therefore handles such units in a separate testing procedure.

Why does the control unit A2139009022 fail?

Stored crash data is the most common cause, even if the event did not trigger an airbag, and a normal diagnostic tool cannot erase it. Aged electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes, for example from a weak battery or jump-starting, are also added.

Crash data is created even in events that do not lead to triggering. It remains in the unit until it is removed during the repair.

Aged components and cold solder joints become prone to faults over time. Moisture and corrosion attack the contacts, which can lead to unstable signals.

Voltage spikes affect the electronics when the battery is weak or a jump-start cable is connected.

How can you tell that the A2139009022 is defective?

The airbag warning light in the instrument cluster stays on permanently or intermittently, an error message appears on the display, the diagnostic tool cannot find the control unit, and the fault memory cannot be cleared. In such a state, airbags and seatbelt pretensioners may not trigger in an emergency.

The warning light is the clearest sign here. If it lights up while driving, there is a fault in the system that must be checked.

A missing connection to the diagnostic tool is also a sign that can be investigated further.

Which vehicles is the A2139009022 fitted in?

The airbag control unit A2139009022 is fitted in these vehicles: Mercedes-Benz E-Class S213 Estate (2016-2023) and W213 Saloon (2016-2023). The selection covers the models for which this control unit is known.

The vehicles with this control unit follow for classification.

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

Compare the part number on the label of the removed unit with this page. That only shows it is the right unit. Also have the fault memory read out beforehand, because only the result shows whether the control unit itself is defective or whether a plug or cable is 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 A2139009022 work?

First have the fault memory read out and attach the log, then disconnect the battery and only then remove the control unit A2139009022. You create the repair order online and send in the packed unit. Testing, repair and the function test at Airbag24 usually take 3–4 working days.

Airbag24 tests the unit on the test bench and specifically repairs the defective components. The stored crash data is erased, then a function test follows. The repaired unit then 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 A2139009022 get to Airbag24?

You send the unit as a parcel to Airbag24 or book a UPS collection for an extra charge. After the repair, UPS brings the unit from Airbag24 back to you.

Put the printed repair order into the parcel and pack the control unit shock-proof.