Airbag control unit with part number A2049012604

What is the function of the airbag control unit A2049012604?

The airbag control unit A2049012604 is the central control module for the occupant safety system (SRS) in the Mercedes-Benz C-Class W204. It carries the manufacturer’s reference 5WK44740 from Continental/Siemens and is responsible for evaluating signals from crash sensors and, in the event of a collision, deploying the airbags and seatbelt pretensioners.

As an OEM part (Original Equipment Manufacturer), this module is precisely tailored to the vehicle architecture of the W204 sedan. It continuously monitors all connected components—such as seat occupancy sensors, seatbelt buckles, and the steering wheel winding spring—to ensure occupant safety at all times.

Proper functionality is critical for the vehicle’s passive safety. In case of a malfunction or internal fault, the entire airbag system is often deactivated preventatively to avoid false activations, while the SRS warning light alerts the driver to the issue.

Why does the control unit A2049012604 fail?

Failures in the A2049012604 control unit frequently arise from stored crash data after an accident, which prevents further use. Other causes include internal hardware defects on the circuit board, such as faulty memory chips (EEPROM/Flash), cold solder joints, or damaged SMD components like voltage regulators and capacitors.

A common reason for failure is the storage of accident data. After a deployment event, the module locks itself internally and cannot be reset using standard diagnostic tools. This is a manufacturer‑specified safety mechanism that requires professional inspection and repair.

Internal hardware faults are another typical cause. These include defects in microcontrollers or memory chips, leading to errors such as B220800 (internal boot or memory error). Issues with the power supply on the circuit board or a deleted Vehicle Identification Number (VIN) following voltage fluctuations also fall into this category.

Often, an internal defect results in the control unit no longer communicating via the OBD2 interface. The workshop can then neither perform diagnostics nor read out the fault memory, indicating a deeper problem within the module itself—provided the CAN bus wiring remains intact.

How do you recognize a fault in the airbag control unit A2049012604?

A defective airbag control unit A2049012604 primarily manifests as a permanently illuminated airbag or SRS warning light on the instrument cluster. Communication with the control unit via a diagnostic tool is often impossible as well. Stored crash data that cannot be erased serves as another clear indicator.

The most obvious sign is the activated SRS warning light. It fails to extinguish after starting the vehicle, signaling that the passive safety system is disabled and that the vehicle will not pass the main inspection (HU/TÜV) due to this deficiency.

Another critical symptom is the complete loss of diagnostic communication. When a workshop attempts to read the fault memory, it receives no response from the control unit, effectively isolating the fault directly to the module itself.

Following an accident or a voltage surge, error codes may remain stored in memory and prove impossible to clear. This points to locked crash data requiring expert repair of the control unit. Work on the airbag system should always be performed exclusively by qualified personnel.

In which vehicles is the control unit A2049012604 installed?

The airbag control unit with part number A2049012604 and manufacturer’s reference 5WK44740 is specifically designed for models of the Mercedes-Benz C-Class. Airbag24 offers professional repair services for this control unit, which is installed in the model series listed below.

At Airbag24, we repair the A2049012604 control unit for the following vehicle model:

Mercedes-Benz: C-Class W204 Sedan (model years approx. 2007–2014)

How does the repair of the control unit A2049012604 proceed?

The repair of the A2049012604 control unit at Airbag24 includes a detailed incoming inspection, hardware analysis, and targeted restoration. Defective components are replaced, cold solder joints are reworked, and, if necessary, stored crash data is safely reset. All repairs come with a final functional test and a 12-month warranty.

After submission to Airbag24, the control unit undergoes a standardized process. First, a visual inspection is carried out, and communication over the CAN bus is tested. An accompanying diagnostic report is essential to quickly narrow down the fault and rule out peripheral issues (e.g., sensors).

In the next step, technicians analyze the circuit board at the component level. Voltage regulators, capacitors, and memory chips (EEPROM/Flash) are inspected. Defective components are replaced professionally, and cold solder joints are re-soldered to restore the original functionality.

Where technically and legally permissible, stored crash data is erased. If necessary, the correct Vehicle Identification Number (VIN) and vehicle-specific coding are restored to ensure full compatibility with the vehicle.

Following successful repair, a final inspection is performed. Airbag24 provides a 12-month warranty on the completed repair. After reinstalling the unit in the vehicle, the fault memory must be cleared, and a self-test of the airbag system should be conducted.

What shipping options does Airbag24 offer?

Airbag24 offers flexible shipping options for your control unit. You can either send the package yourself free of charge or arrange a paid UPS pickup. For returns, you have access to free UPS standard shipping as well as faster express and cash-on-delivery options. Self-collection is also available.

For outbound shipments, you can either ship the removed control unit to us yourself or conveniently book a UPS pickup at your preferred location.

When returning the item, you can choose from several options to suit your needs:

UPS standard shipping is free of charge.

For faster delivery, UPS express shipping is available.

Both standard and express shipping can also be selected with the cash-on-delivery option.

Alternatively, you can pick up the repaired control unit in person at our facility.