Airbag control unit with part number 2123BB106

What is the function of Airbag Control Unit 2123BB106?

The part number 2123BB106 refers to an airbag control unit designed for the Peugeot 107. Its primary task is to monitor the entire occupant protection system. It processes signals from acceleration sensors and, in the event of a crash, controls the deployment of airbags and seatbelt pretensioners to ensure the safety of vehicle occupants.

As the central processing unit of the passive safety system (SRS – Supplemental Restraint System), this control unit remains constantly active. At every vehicle start-up, it performs a self-test to verify the functionality of all connected components, such as airbag modules, seatbelt pretensioners, seat occupancy mats, and crash sensors. If a fault is detected, the airbag warning light on the instrument panel illuminates.

The control unit’s hardware is engineered to operate reliably even under extreme conditions. However, technical service documentation—such as detailed wiring diagrams or component layouts—is typically not publicly available and remains reserved for manufacturers or specialized repair shops.

Why does Control Unit 2123BB106 fail?

Failures of Control Unit 2123BB106 are usually caused by electronic issues, such as internal short circuits, voltage spikes, or undervoltage due to a faulty battery. Physical factors like moisture and corrosion—often exacerbated by the installation location—as well as stored, non‑erasable crash data following an accident are also common causes of failure.

A major reason for repairs is stored crash data. After an airbag deployment, the control unit locks itself internally to prevent unintended re‑deployment. In many cases, this lock can only be reset through professional electronic diagnostics at the component level.

Electrical disturbances in the vehicle’s electrical system are another frequent source of problems. Overvoltage damage—for example, from jump-starting—or persistent undervoltage caused by an aging battery or a defective alternator can harm sensitive electronic components, such as voltage regulators or microcontrollers on the circuit board.

Environmental factors also play a role. For instance, if the control unit is mounted beneath a seat, penetrating moisture can lead to corrosion on connectors and the circuit board, causing leakage currents and ultimately device failure. Similarly, cable breaks or faulty connectors can disrupt communication and trigger error codes.

How do you recognize a defect in 2123BB106?

A defective Airbag Control Unit 2123BB106 primarily manifests as a permanently illuminated airbag or SRS warning light on the instrument panel. Often, communication with the control unit via a diagnostic tool is impaired, or specific, non‑erasable error codes—such as “internal control unit error”—are displayed.

The most obvious symptom is the activated warning light, signaling a malfunction in the safety system and making it impossible to pass the main inspection (HU/TÜV). In this state, the system is typically disabled, posing a significant safety risk in the event of a crash.

Another clear indication is when the workshop’s diagnostic equipment cannot establish a connection with the airbag control unit. The unit no longer responds to requests, suggesting a severe internal hardware failure or a disrupted power supply.

Specific error codes are often stored in the fault memory and cannot be cleared. These include messages about an internal fault or permanently saved crash data that remain even after repairing accident‑related damage to the vehicle.

In which vehicles is Control Unit 2123BB106 installed?

The airbag control unit with part number 2123BB106 is specifically used in the Peugeot 107. At Airbag24, we repair this control unit for all generations and facelifts of this model, offering a reliable and cost‑effective solution for restoring the safety system.

Specifically, repairs are available for the following model variants:

Peugeot 107 I (model years 2005–2009)

Peugeot 107 I 1st Facelift (model years 2009–2012)

Peugeot 107 I 2nd Facelift (model years 2012–2014)

How is 2123BB106 professionally repaired?

After sending the unit to Airbag24, the repair of 2123BB106 begins with an initial inspection and analysis of the attached fault report. This is followed by electronic restoration at the component level, where defective parts are replaced and crash data is reset. A final functional test ensures quality before the unit is returned with 2 years' statutory liability for defects.

The process begins with diagnosis. A fault‑memory readout log provided by the customer is essential for targeted fault analysis. In the workshop, the control unit undergoes a visual inspection, and the fault memory is read again to verify the fault pattern.

The core repair takes place on the circuit board. Technicians replace defective components such as voltage converters or cracked SMD parts, perform precise soldering, and eliminate corrosion damage. Stored crash data is analyzed and, where appropriate and technically feasible, erased or reset using specialized procedures.

Following restoration, a final functional test is conducted. Only after successful testing is the control unit approved for return shipment. It is crucial that, after reinstallation in the vehicle, the fault memory is read and cleared again to ensure the system’s full functionality. Improper self‑repairs or the use of airbag simulators are strongly discouraged, as they pose a serious safety risk and may result in the loss of operating approval.