Airbag control unit with part number 985105123R

What is the function of the airbag control unit 985105123R?

The airbag control unit with part number 985105123R is the central control module for the occupant protection system in the Renault Captur I (model years 2013–2019). It analyzes data from crash sensors and, in the event of a collision, deploys the airbags and pretensioners to protect vehicle occupants.

As the “brain” of the passive safety system, this unit continuously processes signals from the vehicle’s acceleration sensors. When a collision exceeds predefined threshold values, it sends ignition commands to the relevant airbag modules and seatbelt pretensioners within milliseconds.

Its proper functioning is critical for safety, as a failure or malfunction could prevent the restraint systems from deploying correctly in an emergency.

What defects occur in 985105123R?

The most common defect in the 985105123R control unit arises after a crash, when crash data is permanently stored in its memory. This lock cannot be cleared using standard diagnostic tools. Other causes include internal electronic faults, such as error code C1605, which indicates defective components or memory issues.

After airbags or seatbelt pretensioners have been deployed, a so‑called “crash record” is written into the control unit’s internal memory. This entry locks the device’s functionality and serves as a safety measure to force a full system check. The manufacturer does not allow simple deletion via diagnostics.

Besides accidents, individual electronic components—such as processors, EEPROM memory chips, or capacitors—can also fail. These internal malfunctions are often logged in the fault memory with specific codes like C1605 (“Test not completed”), pointing to hardware defects within the unit itself.

Related control unit variants with similar part numbers, such as 985103425R, may also exhibit these typical failure patterns.

How do you recognize a defect in 985105123R?

A defect in the 985105123R control unit typically manifests as a constantly illuminated airbag warning light on the instrument cluster. Often, the control unit can no longer be accessed via the OBD interface, making workshop diagnostics impossible. Stored error codes that cannot be cleared are a clear indication.

The primary and unmistakable symptom is the active airbag warning lamp, signaling to the driver that the passive safety system is inoperative and may fail to deploy in the event of a crash.

In many cases—especially after an accident—the control unit refuses communication with external diagnostic equipment. Workshops are then unable to read or erase the fault memory, indicating an internal blockage caused by crash data.

If an internal fault such as C1605 is detected, this confirms a defect directly within the control unit itself. Such errors cannot be resolved without electronic repair of the hardware.

In which vehicles is 985105123R installed?

The airbag control unit with part number 985105123R is specifically designed for the first-generation Renault Captur. At Airbag24, we repair this control unit for all variants of this model series. Related part numbers, such as 985103425R, are also supported.

Specifically, this control unit is found in the following model:

Renault: Captur I (Type R, model years 2013–2019)

Due to its specialized design tailored to the Captur I’s electronic architecture, it is crucial to verify exact part-number compatibility during repairs or replacements.

How is 985105123R professionally repaired?

Upon submission to Airbag24, the 985105123R control unit undergoes a thorough electronic analysis. The repair process includes erasing stored crash data, replacing defective electronic components with genuine OEM parts, and restoring circuitry. Finally, a functional test ensures full operational readiness. Two years' statutory liability for defects is provided on the repair.

The repair procedure at Airbag24 is standardized and aims to fully restore the original factory specifications. First, the fault memory is read to confirm the exact cause—whether crash data or an internal fault.

Next, crash data is reset at the hardware level. For internal faults, defective components such as memory chips or processors are replaced with high-quality OEM parts, and damaged traces are repaired. Optionally, a software update may be applied if available.

After repair, the control unit undergoes a comprehensive functional test. The unit is only returned once it meets all factory‑specified requirements. Repair offers a cost‑effective and sustainable alternative to expensive new purchases.