Airbag control unit with part number A2139019302

What does the airbag control unit A2139019302 do?

The airbag control unit A2139019302 controls the restraint system (SRS) in vehicles of the brand Mercedes-Benz. It checks the crash sensors and the firing circuits continuously and decides in an accident, within a fraction of a second, which airbags and seatbelt pretensioners are activated.

The unit detects faults itself and shows them via the airbag warning light in the instrument cluster. After an accident, it stores crash data and locks itself.

Why does the control unit A2139019302 fail?

The crash data is the most common cause: it is stored after an accident, even if no airbag has deployed, and a normal diagnostic tool cannot erase it. Added to this are aged electronic components, cold solder joints, moisture and corrosion at plug connections, and voltage spikes from a weak battery or a jump start.

The unit stores the crash data regardless of whether an airbag has deployed. Because an ordinary diagnostic tool does not remove it, the fault stays visible in the fault memory.

The other causes act gradually. Aged components and cold solder joints lead to contact problems, moisture and corrosion attack plug connections, and voltage spikes stress the electronics.

How can you tell that the A2139019302 is defective?

A defect shows up as the airbag warning light in the instrument cluster lighting up constantly or intermittently, as an error message, and as a missing connection to the diagnostic tool. In a critical situation, the airbags and seatbelt pretensioners may then not be able to deploy.

If the warning light comes on while driving, the next step is to read out the fault memory. If it stays on after the ignition is switched on, a fault has been detected.

If the connection to the diagnostic tool is missing, the cause is not necessarily the control unit, because cables and connectors can also interrupt the contact.

Which vehicles is the A2139019302 fitted in?

The control unit A2139019302 is fitted in these vehicles: Mercedes-Benz E-Class S213 Estate (2016-2023) and W213 Saloon (2016-2023).

These models are on record for this part number:

• 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 only confirms that it is the correct unit. Have the fault memory read out beforehand; only this result shows whether the control unit is defective or whether a connector 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 A2139019302 work?

First have the fault memory read out and attach the log, then disconnect the battery and remove the control unit. Afterwards create a repair order online and send the well-packed unit in. Checking, repairing and testing at Airbag24 usually takes 3–4 working days.

The sequence is mandatory for safety reasons, which is why the removal only takes place after the battery has been disconnected.

On the test bench, defective components are replaced at Airbag24, the crash data is erased, and the unit is then function-tested. The unit then comes 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 A2139019302 get to Airbag24?

You send the control unit A2139019302 as a parcel, or book a UPS collection for an extra charge, and after the repair Airbag24 returns it by UPS.

Put the printed repair order in the parcel and pack the unit shockproof.