Description
Airbag control unit for CITROËN C4 first series. The unit is fully functional.
Product Overview
High-quality airbag control unit (SRS/ACU) designed for Citroën C4 (first generation). This unit monitors crash sensors, seatbelt pretensioners and airbag deployment circuits, and issues deployment commands in the event of an impact. Supplied with OEM reference numbers for easy identification and direct replacement in compatible vehicles.
Key Benefits
- Direct fit for many Citroën C4 I models — simplifies replacement and reduces downtime.
- OEM product codes included in the listing for faster search and verification.
- Essential safety component: restores SRS system functionality when faulty or previously deployed unit is replaced.
How It Works
The airbag control unit continuously monitors inputs from impact sensors, occupant sensors and seatbelt buckle sensors. On detecting a severe collision pattern, the unit triggers the appropriate airbags and pretensioners within milliseconds. It also records fault codes and crash events that help diagnose system status after an incident.
Replacement Procedure
Basic replacement steps for experienced mechanics or competent DIYers:
- Disconnect the negative battery terminal and wait at least 10–15 minutes to discharge residual power in the SRS circuits.
- Locate the unit (position varies with trim—commonly mounted under the centre console, beneath the passenger seat or behind the glovebox).
- Remove necessary trim panels and secure fixings to access the control unit.
- Carefully unplug the electrical connectors; avoid pulling on wiring and protect connector latches.
- Unbolt the unit, replace with the new unit and reconnect connectors, ensuring a firm fit.
- Reassemble trim, reconnect the battery and perform a full SRS system scan and fault clear with a compatible diagnostic tool.
Technical Information
- Manufacturer: Stellantis (Citroën)
- Model: Citroën C4 I (First Series)
- Product Codes: 9653493780, 603726100
- Additional Numbers: 654635, 654636
Installation Recommendations
- Always isolate the battery before starting work and follow the vehicle manufacturer’s procedure to prevent accidental airbag deployment.
- Handle the unit and connectors with care to avoid electrostatic discharge and mechanical damage.
- After installation, use a compatible diagnostic tool (for PSA vehicles e.g. DiagBox/Lexia/PP2000) to read and clear SRS fault codes and verify correct operation of the system.
- If the unit has recorded crash data or deployment history, follow legal and safety regulations regarding replacement.
Why This Part Fails
Common causes of airbag control unit failure include: impact/crash events that trigger deployment, water ingress or corrosion damaging internal electronics, connector corrosion or wiring faults, and electrical surges. In many cases the unit remains serviceable unless it has been involved in a collision or exposed to moisture.
Notes For Buyers
Match the OEM part numbers listed above with the vehicle’s original part marking to ensure compatibility. This listing includes primary OEM references used on first-series Citroën C4 models.
