Airbag control unit with part number 5WK44740

What is the Airbag Control Unit 5WK44740?

The Airbag Control Unit 5WK44740, manufactured by Siemens/Continental, serves as the central control module for the occupant protection systems in the Mercedes-Benz C-Class W204. It processes data from crash and acceleration sensors to deploy the appropriate airbags and seatbelt pretensioners within milliseconds, ensuring passenger safety.

As the brain of the entire SRS (Supplemental Restraint System), this control unit is responsible for monitoring, analyzing, and activating all passive safety components. Based on incoming sensor data, it determines which restraint systems need to be deployed and at what intensity.

The electronic component carries the manufacturer’s part number 5WK44740 and is typically listed under OE numbers A2049012604 or, in related contexts, A2049012704 at Mercedes-Benz. Failure of this unit inevitably results in deactivation of the entire airbag system.

In case of a malfunction, the airbag warning light illuminates, the entire protection system becomes inoperative, and the vehicle fails its mandatory technical inspection (HU). Prompt repair is therefore both safety‑ and registration‑relevant.

What Defects Occur in the 5WK44740?

Typical defects in the 5WK44740 control unit include permanently stored crash data after an accident, as well as internal hardware failures on the circuit board. The latter often manifest as error code B220800 (a severe internal fault) and affect components such as memory chips or the power supply.

A very common reason for repair is the storage of crash data. Following a collision, these event records are permanently saved in the internal EEPROM/Flash memory and cannot be erased using standard workshop diagnostics (OBD). Specialized electronics shops can reset this data with developer tools.

Internal hardware faults represent another major cause of failure. Error code B220800 directly indicates a problem within the control unit itself—such as defective voltage regulators, memory modules, driver ICs, or faulty solder joints on the circuit board. These issues may occur even without an accident.

In rarer cases, software or coding errors may also arise, leading to communication malfunctions or causing the vehicle identification number to no longer be correctly registered in the control unit. Experts generally consider the 5WK44740 control unit highly repairable.

How Do You Recognize a Fault in the 5WK44740?

A defect in the 5WK44740 control unit primarily manifests as a continuously or intermittently illuminated airbag or SRS warning light on the instrument cluster. Often, communication with the control unit via diagnostic equipment also ceases, or specific internal error codes like B220800 are logged.

The most obvious symptom is the active airbag warning light, signaling to the driver that the passive safety system is inoperable and would not activate in the event of a crash.

Another clear indication is complete loss of communication. When a workshop attempts to read the fault memory, the diagnostic tool receives no response from the airbag control unit, pointing to a serious internal fault.

Entries stored in the fault memory, such as “B220800 – Internal Airbag Control Unit Error,” directly indicate a hardware or internal software issue. Messages like “Side Sensor Error” or the inability to clear errors after replacing peripheral components such as the coil spring may also point to the control unit as the root cause.

In Which Vehicles Is the 5WK44740 Installed?

The airbag control unit with part number 5WK44740 is specifically designed for the Mercedes-Benz C-Class W204 model series (sedan), produced roughly between 2007 and 2014. At Airbag24, we professionally service this control unit for models such as the C 220 CDI, C 320 CDI, and C 350.

At Airbag24, we repair the 5WK44740 part number for the following vehicle models:

Mercedes-Benz: C-Class W204 Sedan (circa 2007–2014)

Is Repairing the 5WK44740 Worth It?

Repairing the 5WK44740 airbag control unit is a technically sound and economically attractive alternative to costly replacement. It is significantly cheaper than purchasing a new original part. Moreover, the vehicle‑specifically coded original unit remains intact, eliminating the need for time‑consuming reprogramming procedures.

A key advantage is the substantial cost savings compared to a new part, which frequently represents an expensive replacement. The repair addresses the underlying electronic cause without requiring full device replacement.

Since the original control unit stays installed in the vehicle, the repair avoids the need for complex reprogramming or SCN coding that would otherwise be required when replacing with a new or used unit. This saves both time and additional workshop expenses.

For every repair performed on your control unit, you also receive 2 years’ statutory liability for defects, underscoring the reliability of the restoration.

How does the repair of the 5WK44740 proceed?

The repair process at Airbag24 begins with the professional removal of the 5WK44740 control unit, ideally accompanied by the included diagnostic report. Upon receipt, technicians analyze the hardware, clear crash data, and rectify electronic faults before testing the unit on a test bench and returning it with 2 years’ statutory liability for defects.

Before removal, the workshop should read out the fault memory to rule out external sources of error, such as defective sensors, the coil spring, or wiring issues. A printout of the fault log should be enclosed with the control unit upon submission to expedite analysis.

Once the control unit arrives at Airbag24, specialized technicians conduct a thorough examination. Depending on the nature of the fault, stored crash data is cleared, defective electronic components on the circuit board are replaced, solder joints are reworked, or software and coding issues are resolved.

Following the repair, a comprehensive functional test is carried out on a dedicated test bench. Here, proper communication and the operation of inputs and outputs are simulated to verify successful repair.

After return shipping and reinstallation in the vehicle, typically only the fault memory needs to be cleared. The airbag system is then fully operational again.