Airbag control unit with part number 985104870R

What is the function of the airbag control unit 985104870R?

The airbag control unit with part number 985104870R, often manufactured by Autoliv, serves as the central control module for the occupant protection system in vehicles such as the Renault Mégane IV and Kadjar. It processes signals from crash sensors to precisely deploy airbags and tighten seat belts in the event of a collision.

As the “Airbag Sensor Module,” this component acts as the brain of the entire safety system. It continuously monitors all connected components—from impact sensors located at the front and sides of the vehicle to individual airbag modules and seatbelt pretensioners.

The proper functioning of this control unit is critical, as it determines whether passive safety systems are activated during an accident. It is also listed under the alternative part number 640443200B and is specifically designed for the electronic architecture of the Renault Mégane IV (from 2016 onward) and related models.

Why does the control unit 985104870R fail?

The most common cause of failure for the 985104870R control unit is the storage of crash data after an accident, which locks the device. Other reasons include internal electronic malfunctions in hardware components, as well as physical damage—such as water ingress.

Following a collision, the control unit permanently stores so‑called crash data. This is a manufacturer‑specified safety measure that prevents reuse without professional inspection and repair. As a result, the unit becomes locked and must be professionally reset.

In addition, purely electronic faults can occur. Internal board defects, faulty processors, or damaged memory chips may trigger error codes such as “Control Unit Fault” or “Internal Error.” These issues stem from hardware problems and require component‑level repairs.

A further, not uncommon cause is external factors like water damage. Moisture penetration leads to corrosion at solder joints and electronic components, potentially causing short circuits and complete failure of the control unit.

How do you recognize a defect in the 985104870R?

A defect in the airbag control unit 985104870R almost always manifests as a constantly illuminated airbag warning light on the instrument panel. Additionally, diagnostic tools may no longer communicate with the control unit, or specific error codes such as “Internal Error” may appear.

The primary and unmistakable sign of a problem is the red airbag warning light. If this light remains on after starting the engine, it indicates a critical fault, rendering the airbags non‑functional in the event of an accident.

In the workshop, suspicion is confirmed when a diagnostic tool cannot establish communication with the airbag module. Such a loss of connectivity points to a severe internal malfunction of the control unit.

If error codes like “Control Unit Fault” or “Crash Data Stored” are logged in the fault memory, the root cause is clearly attributable to the control unit itself. These messages necessitate targeted module repair.

In which vehicles is the 985104870R control unit installed?

The airbag control unit 985104870R is primarily used in various Renault models. Key examples include the fourth‑generation Renault Mégane from 2016 onward—including the sporty RS variant and the Grandtour—as well as the Renault Kadjar.

At Airbag24, we regularly repair part number 985104870R for the following specific vehicle models:

Renault: Mégane IV (from 2016), Mégane RS IV, Mégane IV Grandtour, and Kadjar. Compatibility covers the entire model range of these vehicles, which utilize this particular Autoliv control unit.

How does the repair of the 985104870R proceed at Airbag24?

The repair process at Airbag24 begins with removing and shipping the defective control unit. Following a detailed analysis, faults—such as stored crash data or defective components—are rectified. A final functional test ensures full operational readiness, backed by 2 years' statutory liability for defects.

After carefully removing the unit from the vehicle, please pack it securely and send it to Airbag24. Upon receipt, the device is immediately registered to ensure prompt processing.

Our technicians perform a comprehensive diagnosis to identify the exact cause of the issue. Depending on the findings, they initiate the necessary repair steps, including professional resetting of stored crash data or replacing faulty electronic components on the circuit board.

Once repaired, each control unit undergoes rigorous functional testing on a specialized test bench. This guarantees that the device once again meets all manufacturer‑specific requirements. Of course, every completed repair comes with 2 years' statutory liability for defects.