Airbag control unit with part number A0025428118

What is the function of the airbag control unit A0025428118?

The airbag control unit A0025428118 is a central safety electronic component manufactured by TEMIC, specifically designed for the Mercedes-Benz ML-Class W163. It is mounted on the vehicle floor beneath the center console and controls the entire passive restraint system, including all airbags, seatbelt pretensioners, and seat occupancy detection, to ensure optimal occupant protection in the event of a crash.

As the “brain” of the SRS (Supplemental Restraint System), this control unit continuously processes data from acceleration and crash sensors. Based on this information, it determines within milliseconds whether a collision has occurred and which restraint devices need to be deployed.

The proper functioning of the A0025428118 control unit is critical for vehicle safety. If it fails or malfunctions, the entire airbag system becomes disabled, which can have severe consequences in a collision. Therefore, a lit SRS warning light is always a serious warning sign.

Why does the airbag control unit A0025428118 fail?

The most common cause of failure for the A0025428118 control unit is internally stored crash data after an accident, which often cannot be cleared via diagnostics. Another major cause is internal electronic defects, indicated by error code B1000 (“control unit defective”). These issues arise due to component aging, vibrations, or moisture exposure at the installation location.

A key problem is the storage of crash data. After an airbag deployment, the control unit locks itself internally to prevent reuse. In many cases—especially with the W163—this lock cannot be reset through the OBD interface. Professional repair requires direct access to the memory chips (EEPROM/Flash) on the circuit board.

Error code B1000 points to an irreparable internal fault, often caused by defective microprocessors, memory chips, or problems with the power supply. Cold solder joints or corrosion on connector pins—exacerbated by the unit’s low mounting position in the vehicle tunnel—can also lead to intermittent or permanent failures.

In practice, a misleading diagnostic picture often emerges: the scan tool reports faulty seatbelt pretensioners or ignition circuits, even though their resistance values (typically 2–4 Ω) and wiring are intact. This clearly indicates that the control unit itself is misinterpreting signals, making it the root cause of the issue.

How do you recognize a defective A0025428118?

The clearest symptom of a defect in the A0025428118 control unit is the permanently illuminated red airbag or SRS warning light in the instrument cluster. Often, fault codes stored in the error memory—particularly B1000—cannot be cleared using a diagnostic tool. This inevitably results in failing the main inspection (HU/TÜV).

The airbag warning light is the system’s direct indication that a malfunction exists and protective functions are no longer guaranteed. It illuminates upon starting the vehicle and does not extinguish as expected.

Another clear sign is when, after an accident and replacement of all deployed components (airbags, seatbelt pretensioners), the warning light remains on. This suggests that crash data stored and locked within the control unit persists.

During workshop diagnostics, the issue often manifests as readable fault codes that reappear immediately after attempts to clear them. In some cases, communication with the control unit may become impossible altogether.

In which vehicles is A0025428118 installed?

The airbag control unit with part number A0025428118 was primarily used in the first generation of the Mercedes-Benz ML-Class. At Airbag24, we specialize in repairing this specific control unit for the following model, offering a cost-effective and reliable solution.

Mercedes-Benz:

ML-Class W163 SUV (model years approx. 1997–2005)

Although some sources suggest use in other models, its primary application is unequivocally the Mercedes ML-Class W163. Repairing this unit here provides a proven alternative to the expensive purchase of a new original part.

How does repair of the A0025428118 work at Airbag24?

After sending your removed control unit to Airbag24, we perform a professional analysis. The repair includes erasing crash data at the hardware level and fixing internal electronic faults. Since your original unit is repaired, the vehicle’s coding remains unchanged. We provide 2 years' statutory liability for defects on every repair.

The process ideally begins in your workshop with a thorough diagnosis. Read out the fault memory and inspect the peripherals (cables, sensors) to confirm that the fault truly lies within the control unit. Please include a printout of the fault codes with your package.

After professional removal, send the unit securely packaged to Airbag24. Our technicians will perform an initial inspection to verify the reported fault. Subsequently, the stored crash data is directly erased from the memory chip, and any defects in the electronics—such as faulty components or solder joints—are repaired.

A key advantage of repair is preserving the original VIN and vehicle configuration. Replacing the unit with a used one often requires time-consuming re‑coding, which is unnecessary here. Following restoration, a final test is conducted on our test bench, simulating all functions under real‑world conditions.