Airbag control unit with part number A1729015805

What is the function of the airbag control unit A1729015805?

The airbag control unit A1729015805 is the central control module of the occupant protection system (SRS) for the Mercedes-Benz SLK-Class R172 and SLC R172. It processes data from crash sensors in real time to precisely deploy airbags and seatbelt pretensioners in the event of a collision, while also storing relevant event data.

As the “brain” of the passive safety system, this module—also known as the SRS module—is responsible for monitoring and evaluating signals from acceleration and pressure sensors throughout the vehicle. In the event of a collision, the control unit determines within milliseconds which restraint systems—such as front, side, or head airbags, as well as seatbelt pretensioners—need to be activated to provide optimal occupant protection.

Following an accident, the unit permanently stores so‑called crash data. This feature is crucial for accident analysis but also results in the control unit being locked out for further operation, even if no visible damage is present.

Why does the control unit A1729015805 fail?

A failure of the A1729015805 control unit is usually caused by crash data stored after an accident (error code B1000), which locks the module. Other causes include internal electronic malfunctions or a complete loss of communication. Equivalent part numbers are A1729017601, A1729019102, and A1729015704.

The most common cause of malfunction is the storage of crash data. After airbags or seatbelt pretensioners have deployed, the control unit is electronically blocked for safety reasons. The error code B1000 stored in the fault memory explicitly indicates this condition.

Another type of failure manifests as a complete breakdown in communication. In such cases, no diagnostic connection can be established with the control unit, pointing to a serious internal electronic fault. These issues may occur spontaneously or result from external factors like water damage.

Spontaneous failures due to aging electronic components or board-level defects can also occur, leading to internal error messages and deactivation of the entire airbag system. It’s important to note that the part number listed here can be replaced by equivalent numbers—A1729017601, A1729019102, and A1729015704—which were often used in later model years.

How do you recognize a defect in the A1729015805?

A defective A1729015805 control unit primarily shows up as a continuously illuminated airbag warning light on the instrument cluster. Often, the unit cannot be read using a diagnostic tool (no communication), or error codes such as B1000—indicating an internal fault or stored crash data—are displayed.

The clearest symptom is the persistently lit airbag warning light (SRS light). It does not turn off after starting the vehicle, signaling to the driver that the occupant protection system is not operational. In the event of a crash, there is a risk that the airbags will fail to deploy.

During workshop diagnostics, it is frequently observed that no communication can be established with the control unit. The diagnostic tool receives no response from the module, making precise fault analysis impossible and indicating a total system failure.

If communication is possible, specific error codes are retrieved. Code B1000 clearly points to stored crash data following an accident, while other codes may indicate non-specific internal hardware malfunctions.

In which models is the A1729015805 control unit installed?

The airbag control unit with part number A1729015805 is specifically installed in convertible models from Mercedes-Benz. At Airbag24, this module is professionally refurbished for the Mercedes-Benz SLK-Class of the R172 series (2011–2016) and the Mercedes-Benz SLC-Class of the R172 series (2016–2020).

At Airbag24, we repair part number A1729015805 and its variants for the following vehicles:

- Mercedes-Benz SLK-Class R172 Convertible (2011–2016)

- Mercedes-Benz SLC-Class R172 Convertible (2016–2020)

How does the repair of the A1729015805 proceed at Airbag24?

At Airbag24, the submitted A1729015805 control unit undergoes a thorough electronic analysis. Technicians reset the stored crash data, resolve internal faults at the component level, and restore the original factory functionality. A final test ensures full operability, backed by 2 years' statutory liability for defects.

After removal from the vehicle and shipment to Airbag24, a standardized and proven repair process begins. First, an initial inspection is performed to verify the reported fault and document the exact condition of the unit.

Electronic repair then follows. Specialized technicians erase the stuck crash data directly from the control unit’s memory and resolve any internal hardware faults. This restores the original functionality without limitations, ensuring the device operates like a brand-new component.

After repair, each control unit undergoes a comprehensive functional test on a simulator. This ensures all communication channels are functioning flawlessly and that no errors remain stored in the memory. Only after passing this test is the unit approved for return shipment, including 2 years' statutory liability for defects on the work performed.