Citroën C4 Cactus I airbag control unit repair

What is a Citroën C4 Cactus I airbag control unit?

If an impact occurs in the Citroën C4 Cactus I, the airbag control unit 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 to do so. During normal driving it monitors the system continuously and indicates faults via the airbag warning light.

The control unit is fitted in the Citroën C4 Cactus I (2014 to 2020); it comes from Bosch. This is where the signals of the entire restraint system are bundled, from the sensor to the firing circuit. Because everything runs through this one unit, a fault is first noticed at the warning light in the instrument cluster.

After an accident, the unit stores crash data and locks itself. The airbag system is then no longer ready for use without a repair.

Why is the Citroën C4 Cactus I airbag control unit defective?

The most common cause is crash data stored in the unit after an accident, even if the airbags did not fire at all. Ageing electronic components, cold solder joints, moisture and corrosion at connectors, or voltage spikes may also be the trigger.

A standard diagnostic tool cannot delete the stored crash data. The electronics themselves are also subject to wear: components age, and solder joints become brittle over time and through constant temperature changes in the vehicle. Voltage spikes can arise, for example, with a weak battery or when jump-starting.

If the airbag warning light stays on, the fault memory cannot be reset or the diagnostic tool cannot establish contact with the control unit, you should have the control unit checked before suspecting other parts of the system.

Common error codes for Citroën C4 Cactus I airbag control unit repair

The codes for the Citroën C4 Cactus I point to internal faults of the control unit, communication failures, an unsuitable supply voltage or faults in the firing circuits. They are read from the fault memory with a diagnostic tool.

These codes are known for the unit; this is not an exhaustive list:

• F620 → Internal control unit fault, not specified
• F633 → Internal fault in the passenger airbag firing system, first stage
• F00F → Control unit no longer transmits on the CAN network
• E650 → Control unit supply voltage too high
• B0001 → Driver airbag firing circuit, first stage: resistance too high
• B0028 11 → Front right side airbag: wiring fault, short circuit to ground
• C601 → Driver airbag firing module, first stage: open circuit

A single code is not enough to say with certainty whether the control unit is defective. An airbag module, a connector or a wire may equally be the cause. Only the inspection of the unit you send in brings clarity.

What part numbers are available for the Citroën C4 Cactus I airbag control unit repair?

You will find the part number, which defines the exact version, on the label of your control unit. Because there are different numbers in the Citroën C4 Cactus I depending on equipment and year of manufacture, it is worth checking the label.

These numbers are known to us for the unit; the list is not complete:

• 98 101 064 80 (Bosch)
• 98 295 355 80 (Bosch)

Compare the number on your unit with the list. This only confirms that you have the right unit in front of you. Whether there is a defect only becomes clear from reading out the fault memory or from the inspection.

The route to repair: first have the fault memory read out, disconnect the battery from the vehicle electrical system and remove the control unit. Then you create a repair order online and send the unit to Airbag24. Airbag24 usually allows 3–4 working days for inspecting, repairing and testing. Your own unit is sent back to you. 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.