Airbag control unit with part number A2139004425

What does the airbag control unit A2139004425 do?

The airbag control unit A2139004425 forms the control centre of the restraint system in the Mercedes-Benz. It captures the signals from the crash sensors, determines in an accident which airbags and seatbelt pretensioners are to be triggered, and continuously checks itself.

The unit detects faults and reports them via the airbag warning light in the instrument cluster. In this way, the vehicle shows the fault.

After an accident, the unit stores crash data and locks itself. Only a repair lifts the lock.

Why does the control unit A2139004425 fail?

The most common cause is stored crash data left in the control unit by an accident, even if no airbag was triggered. A normal diagnostic tool cannot remove it. Added to this are aged components, moisture, cold solder joints and voltage spikes.

Airbag24 erases the crash data during the repair, so that it does not remain in the unit.

Components age over time, solder joints can go cold, and moisture as well as corrosion attack the plug connections. Voltage spikes, for example from a weak battery or a jump start, put additional strain on the electronics.

How can you tell that the A2139004425 is defective?

A defect shows up as an airbag warning light that stays on, as a fault message in the instrument cluster, as a diagnostic tool without a connection and as a fault memory that cannot be cleared. Signs like these must be taken seriously.

• airbag warning light on permanently or intermittently
• fault message in the instrument cluster
• diagnostic tool cannot reach the control unit
• fault memory cannot be cleared

In an emergency, airbags and seatbelt pretensioners may possibly fail to deploy if the control unit is defective. Act promptly, therefore.

Which vehicles is the A2139004425 fitted in?

The A2139004425 is fitted in these vehicles: Mercedes-Benz E-Class S213 Estate (2016-2023) and W213 Saloon (2016-2023).

The following table lists the models recorded for this part number:

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

A comparison of the part number on the label with this page confirms that it is the right unit. The fault memory, however, shows whether the control unit itself is defective or whether a plug or cable is the cause. Have it read out beforehand.

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 A2139004425 work?

Have the fault memory read out first, attach the log and disconnect the battery before you remove the control unit. Then create a repair order online and send in the well-packed unit. Processing at Airbag24 takes 3–4 working days.

Airbag24 checks the unit on the test bench, replaces defective components, erases the crash data and carries out a function test.

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 A2139004425 get to Airbag24?

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

Pack the unit shock-proof and enclose the printed repair order.