Airbag control unit with part number A246 900 75 02

What is the function of the airbag control unit A246 900 75 02?

The part number A246 900 75 02 refers to an airbag or SRS (Supplemental Restraint System) control unit for the Mercedes-Benz B-Class, W246 series. Its primary task is to monitor all components of the passive safety system, evaluate sensor signals during a collision, and precisely activate airbags and seatbelt pretensioners.

As the central control unit, it continuously collects data from acceleration and pressure sensors in the vehicle. In the event of a crash, it determines within milliseconds which restraint systems need to be deployed to provide optimal protection for occupants. After activation, the unit stores relevant crash data, preventing further functionality until inspection and repair.

Why does the A246 900 75 02 control unit fail?

The main cause of failure for the A246 900 75 02 control unit is the retention of crash data after an accident, which blocks further operation. Likewise, defects in electronic components such as SMD parts, processors (BGA), voltage regulators, or corrosion damage can lead to total or partial failure.

A common reason for repair requests is the permanent storage of crash events in the internal EEPROM memory. Even after the vehicle has been repaired, the control unit remains locked, and the airbag warning light stays illuminated. Clearing this data often requires specialized equipment.

In addition, purely electronic faults may occur, including cold solder joints on processors (requiring BGA rework), defective voltage regulators, fuse resistors, or capacitors. Moisture ingress leading to corrosion on the circuit board can also impair or destroy module functionality.

Repair lists frequently list part numbers A246 900 60 18 and A246 900 07 09 as technically similar or compatible, capable of exhibiting comparable fault patterns.

How do you recognize a defect in the A246 900 75 02?

A faulty A246 900 75 02 control unit primarily manifests as a permanently illuminated airbag warning light on the instrument cluster. Communication via the diagnostic interface is often lost, making it impossible to read error codes, and the restraint systems become non-functional.

The most obvious symptom is the persistently lit airbag indicator light. It fails to extinguish after starting the vehicle, indicating a critical system error that constitutes a significant defect during the mandatory technical inspection.

Another clear sign is when a professional workshop cannot establish communication with the airbag control unit using a diagnostic tool. The module no longer responds to queries, rendering precise fault analysis inside the vehicle impossible.

Following a crash—even if not all airbags deployed—the control unit is often internally locked. This results in a persistent warning message and complete loss of safety functions until the stored crash data is professionally reset.

In which vehicles is the A246 900 75 02 control unit installed?

The airbag control unit with part number A246 900 75 02 is specifically designed for the Mercedes-Benz B-Class, W246 series, produced between 2011 and 2018. At Airbag24, we offer professional repairs for this and related control units of this vehicle model.

Repairs are available for the following models and series:

Mercedes-Benz: B-Class (W246)

How does repair work at Airbag24?

At Airbag24, repairing the A246 900 75 02 begins with a comprehensive initial inspection to diagnose the issue. Depending on findings, crash data is either reset or defective hardware components are replaced at the chip level. Following successful restoration and final functional testing, the unit is returned with 2 years’ statutory liability for defects.

Before removing the control unit, it is recommended to read out the fault memory and attach the transmission log. This speeds up diagnosis in our facility.

Upon receiving the unit at Airbag24, a detailed analysis takes place. Our technicians perform visual inspections and electrical tests to pinpoint the exact cause of the fault—whether it’s a software issue caused by crash data or a hardware defect.

Restoration includes, as needed, proper resetting of crash data, replacing defective components through micro-soldering, or repairing complex processor damage (BGA rework). All repairs are carried out to the highest quality standards.

Finally, each control unit undergoes a thorough final check on our test benches to ensure proper CAN-bus communication and flawless operation of all safety-related systems. We provide 2 years' statutory liability for defects on every repair.