Citroën ë-C3 IV airbag control unit repair

What is a Citroën ë-C3 IV airbag control unit?

In an emergency, the airbag control unit of the Citroën ë-C3 IV decides within milliseconds which airbags and seatbelt pretensioners fire. As the central control unit of the restraint system (SRS), it evaluates the signals from the crash sensors for this purpose. During normal driving it monitors the entire system and indicates faults with the airbag warning light.

The control unit is installed in the Citroën ë-C3 IV (since 2024). As long as no accident occurs, it works unobtrusively in the background and continuously tests sensors, firing circuits and the data connection to the other control units. If it finds anything unusual, it signals this via the warning light in the instrument cluster.

If an accident has occurred, the control unit stores crash data and locks itself. The restraint system is then no longer ready, and the light does not go out.

Why is the Citroën ë-C3 IV airbag control unit defective?

Most often the cause is crash data stored in the unit after an accident, even if no airbag was deployed. Ageing electronic components, cold solder joints, moisture with corrosion on the connectors and voltage spikes are also possible triggers.

A standard diagnostic tool does not erase stored crash data. The other causes develop gradually: electronic components wear out, solder joints lose contact, moisture attacks the contacts of the connectors. Voltage spikes occur, for example, with a weak battery or when jump-starting. Often only the warning light is noticed at first.

Signs of a problem are an airbag warning light that stays on permanently, a fault memory that cannot be reset, or a diagnostic tool that cannot establish a connection to the control unit at all. In that case the unit should be checked.

Common error codes for Citroën ë-C3 IV airbag control unit repair

The error codes of the Citroën ë-C3 IV point to different areas: communication in the vehicle network, internal faults of the control unit, the supply voltage and individual firing circuits. They are stored in the fault memory and can be read out with a diagnostic tool.

The following overview shows which messages occur on this model, with a short explanation for each code.

• F620 → Internal control unit fault, not specified further
• F633 → Internal fault in the front passenger airbag firing system, stage one
• F00F → Control unit no longer transmitting on the vehicle network
• E650 → Control unit supply voltage too high
• B0001 → Driver airbag firing circuit, resistance too high
• B0028 11 → Front right side airbag, wiring fault with short circuit to ground
• C601 → Open circuit in the driver airbag firing circuit

A single code does not yet prove a defect in the control unit. A connector, a wire or an airbag module can be the cause just as well. Where the fault actually lies only becomes clear during testing. Keep a record of the codes that were read out, ideally as a log, and enclose it with your repair order.

What part numbers are available for the Citroën ë-C3 IV airbag control unit repair?

On the label of the control unit you will find the part number, which defines its exact version. Depending on equipment and year of manufacture, the numbers differ within a model series, which is why it belongs in the repair order.

No list of known numbers is available for this model so far. Therefore take the number directly from the label of your removed unit and enter it in the repair order. Whether the unit is defective is not determined by the number, but by reading out the fault memory and by testing.

The route to repair: first have the fault memory read out, then disconnect the battery and remove the control unit. After that, create a repair order online and send the unit to Airbag24. Testing, repairing and checking there usually take 3–4 working days. The repaired control unit comes back with all vehicle data and is ready for use as soon as it is refitted — no coding or programming is required.