Airbag control unit with part number A2139007105

What is the Airbag Control Unit A2139007105?

The airbag control unit with part number A2139007105 is the central control module for the passive safety system (SRS) in the Mercedes-Benz E-Class, model series W213 and S213. It monitors all safety‑related components, processes signals from crash sensors, and is responsible for deploying airbags and seatbelt pretensioners in the event of a collision.

As the “brain” of the restraint system, this module continuously communicates with numerous sensors throughout the vehicle. These include acceleration sensors that detect impacts, as well as seat‑occupancy detection mats that report the status of the front passenger side.

Based on this data, the A2139007105 control unit determines within milliseconds which restraint devices need to be activated to provide optimal protection for occupants. The OEM part number is also formatted as A 213 900 71 05 and is uniquely assigned to these vehicle models.

What Defects Occur in A2139007105?

The most common cause of failure for the A2139007105 control unit is the storage of crash data after an accident, which the module locks for safety reasons. Other typical defects are purely electronic in nature, such as cold solder joints, aged components on the circuit board, or communication errors on the CAN bus. Moisture damage can also impair functionality.

Following an airbag deployment, a permanent dataset—known as crash data—is stored in the control unit’s memory. This lock prevents further use and must be professionally reset to restore full system functionality.

Internal hardware faults are another frequent cause of failure. These include defective or aged SMD components, as well as cold solder joints that develop over years due to thermal stress and vibrations in the vehicle, leading to intermittent connections.

Especially in vehicles with leaks or spilled liquids around the center console, corrosion and moisture damage can occur on the circuit board, resulting in short circuits or broken traces.

Communication errors manifest when the control unit becomes unreachable via the CAN bus. The root cause often lies in faulty bus transceivers or defective resistors at the device’s interfaces.

However, repair is not always possible. For irreparable damage to the memory chip (Flash/EEPROM) or central processors (ICs), as well as manufacturer‑imposed locks, replacing the entire unit is frequently the only viable solution.

How Do You Recognize a Fault in A2139007105?

A defective A2139007105 airbag control unit primarily shows itself through the permanently illuminated airbag or SRS warning light on the instrument cluster. Another clear indication is the lack of communication with the control unit during diagnostics, where the device becomes unresponsive via the OBD port.

The most noticeable symptom is the persistently lit SRS warning lamp. It does not turn off after starting the vehicle, indicating a serious, stored error in the system.

When a specialist workshop attempts to read the fault memory, communication with the airbag control unit fails. The system displays it as “unreachable” or “not responding.”

A rarer but very specific symptom is the absence—or “disappearance”—of the vehicle identification number (FIN/VIN) within the module. This points to an internal memory or data integrity issue.

These signs directly indicate an internal defect of the control unit, provided external causes such as faulty sensors, the slip ring, or wiring problems have already been ruled out.

In Which Vehicles Is A2139007105 Installed?

The airbag control unit with part number A2139007105 is specifically used in the Mercedes-Benz E-Class produced between 2016 and 2023. At Airbag24, we offer professional, cost‑effective repair services for this control unit, installed in both sedan and estate variants.

At Airbag24, the A2139007105 control unit is repaired for the following specific vehicle models:

Mercedes-Benz E-Class W213 Sedan (model years 2016–2023)

Mercedes-Benz E-Class S213 Estate (model years 2016–2023)

To ensure exact compatibility, it is crucial to verify the part number stamped on the control unit housing. The number A 213 900 71 05 is identical to A2139007105.

How Does Repair Work at Airbag24?

At Airbag24, repairing the A2139007105 control unit follows a standardized, transparent process. After submission, a detailed analysis is performed, followed by expert hardware restoration or deletion of crash data. A final functional test confirms full operability before returning the unit with 2 years' statutory liability for defects.

Before removal and shipment, we strongly recommend performing a comprehensive vehicle diagnostic and attaching the fault log. This helps to rule out external sources of error, such as defective sensors, seat occupancy mats, or wiring, in advance.

Upon receipt of the control unit at Airbag24, our technicians conduct a thorough incoming inspection. This includes a visual check for physical damage as well as an electronic analysis to precisely locate any faults.

The actual repair process varies depending on the defect: it may involve replacing faulty components, re-soldering problematic solder joints (reflow), or addressing corrosion damage. Where technically feasible and legally permissible, stored crash data is professionally erased.

Finally, each repaired control unit undergoes a rigorous functional test on our test benches. After a successful test, the unit is prepared for return shipment. We provide 2 years' statutory liability for defects on every repair performed.

Please note: Work on the airbag system must only be carried out by qualified specialists. The use of simulators or other improper bypass methods is dangerous and will result in the loss of the vehicle’s operating license.