B00A002 - WSS malfunction (seat occupancy mat defective) airbag control unit fault

What does error code B00A002 mean?

Error code B00A002 indicates a serious internal system fault in the airbag control unit. The cause is usually a hardware defect, such as faulty memory chips, defective capacitors, or damaged solder joints. The control unit can no longer guarantee its safety‑critical functions, which results in the airbag warning light illuminating immediately.

Technically speaking, B00A002 means that the control unit’s internal self‑diagnostic has detected an irreparable fault. This may be caused by defective electronic components like memory chips (EEPROM/Flash) or by voltage spikes, for example from a faulty alternator. As a result, the entire airbag system is deactivated as a precautionary measure.

Although the description sometimes refers to a wheel speed sensor (WSS), in the context of the airbag control unit it almost always signifies an internal, general system error. The unit is no longer able to process sensor signals correctly or deploy the airbags in the event of a crash.

What symptoms are associated with B00A002?

The primary and unmistakable symptom of error code B00A002 is the permanently illuminated airbag warning light (SRS light) on the instrument cluster. This light does not turn off after starting the vehicle. In many cases, the fault memory also cannot be cleared permanently.

The airbag warning light indicates that the entire restraint system is out of service. In the event of a crash, the airbags and seatbelt pretensioners will not deploy, posing a significant safety risk. Consequently, the vehicle is no longer roadworthy.

Another possible symptom is that the diagnostic tool can only communicate with the airbag control unit in a limited capacity or not at all. The internal fault may block regular diagnostic communication via the OBD interface.

What causes B00A002?

The main cause of B00A002 is an internal hardware defect. This includes faulty memory chips, defective capacitors, cold solder joints, or cracks on the circuit board. Stored crash data that cannot be erased after an accident can also trigger this error. External voltage issues are another potential cause.

A common trigger is aging electronic components. In particular, memory chips and capacitors can lose their specifications over time and generate internal data errors. Moisture from water damage can also lead to corrosion and short circuits on the circuit board, resulting in error B00A002.

Voltage problems in the vehicle’s electrical system—such as those caused by a faulty alternator or jump-starting with incorrect polarity—can damage sensitive microprocessors in the control unit. B00A002 often occurs in combination with other error codes, such as B00A087 (faulty message), B1000 (replace control unit), B1010 or B1315 (faulty power supply), as well as the generic code 65535 (control unit defective).

Which models experience B00A002?

Error code B00A002 is especially common in certain Mercedes-Benz models. At Airbag24, we have successfully repaired this error code across various model series, particularly in newer-generation SUVs and pickups featuring complex control electronics.

Our technicians have experience repairing this fault in the following vehicles:

Mercedes-Benz: GLA-Class (X156 SUV, 2013–2020), GLS-Class (X167 SUV, 2019–present), X-Class (X470 pickup, 2017–2020)

How does repair work at Airbag24?

The repair of error B00A002 focuses on eliminating internal hardware and data faults. At Airbag24, the removed control unit is first subjected to a thorough analysis to pinpoint the exact source of the fault on the circuit board. Defective components are then professionally replaced, and crash data is erased.

The process at Airbag24 follows proven steps: After removal at your workshop, you send the control unit to us. Our specialized technicians perform an incoming inspection and identify defective components such as memory chips or capacitors. These are replaced at the chip level.

Subsequently, any existing crash data is completely erased, and the unit is restored to factory settings. Following a final functional test, the repaired control unit is returned to you. Once installed, it is immediately fully operational (plug-and-play), with no need for re‑coding. The vehicle’s fault memory only needs to be cleared once after installation.

This approach offers a cost‑effective and sustainable alternative to the expensive purchase of a new control unit. We provide 2 years' statutory liability for defects on all repairs.