Description
Airbag control unit for Citroën C4 first series. The unit is fully functional.
This SRS airbag control unit (airbag ECU) is a direct-fit replacement for Citroën C4 first generation vehicles and is frequently sought under its part numbers. Designed for professional workshops and experienced DIY mechanics, the unit restores proper airbag system monitoring and fault reporting. Installed correctly, it ensures the vehicle’s supplementary restraint system (SRS) can detect collisions and trigger airbags and seatbelt pretensioners as intended.
Key Features And Benefits
- Direct replacement for original equipment — saves installation time and reduces troubleshooting.
- Comes with common manufacturer product codes to simplify searching and ordering.
- Restores SRS system diagnostics and fault logging for safe operation of airbags and pretensioners.
- Suitable for mechanics and skilled DIYers who follow correct safety and diagnostic procedures.
Technical Information
- Manufacturer: Stellantis (Citroën/Peugeot)
- Model: Citroën C4 I (First Series)
- Product Codes: 9653493780, 603726100
- Other Numbers: 654635, 654636
Installation Recommendations
- Always Disconnect The Battery: Before any work on the SRS system, disconnect the negative battery terminal and wait at least 10 minutes (manufacturer guidance may recommend up to 15 minutes) to allow capacitors to discharge.
- Follow Manufacturer Procedures: Remove interior trim carefully to access the control unit. Keep connectors and locking tabs intact; avoid pulling on wiring.
- Diagnostic Clearing And Initialization: After fitting, clear SRS fault codes and verify system status with a suitable diagnostic tool. If the unit contains crash data, it must be cleared or replaced following proper diagnostic procedures.
- Safety First: Do not attempt to work on the airbag system if you are unfamiliar with SRS safety procedures. Use insulated tools and wear appropriate PPE.
How The Part Works And Why It Fails
The airbag control unit continuously monitors sensors (impact sensors, seat occupancy, belt tensioners) and decides whether to deploy restraint components in the event of a collision. It also logs fault codes that illuminate the SRS warning light on the dashboard when the system detects an issue.
Common Reasons For Failure:
- Crash Impact: Units frequently register non-recoverable crash data after deployment events and then require replacement or professional servicing.
- Water Ingress And Corrosion: Moisture reaching connectors or the unit housing can cause electrical faults.
- Electrical Surges Or Short Circuits: Faulty wiring, poorly fitted jump-starts, or battery issues can damage the ECU electronics.
- Connector Damage Or Loose Contacts: Vibration and improper handling can lead to intermittent faults or permanent failure.
Replacement Procedure (Summary)
- Disconnect Negative Battery Terminal And Wait Minimum 10 Minutes.
- Locate The Unit (Refer To Vehicle Repair Manual For Exact Position), Remove Interior Trim Panels As Needed.
- Unplug Electrical Connectors And Unscrew Mounting Bolts; Remove Old Unit Carefully.
- Install New Unit, Secure Mounting Bolts, Reconnect Connectors Ensuring Proper Locking.
- Reconnect Battery, Use Diagnostic Tool To Clear Fault Codes, Verify That The SRS Warning Light Is Off, And Perform System Self-Test.
Most Common Symptoms Indicating A Faulty Unit
- Persistent SRS Warning Light On Dashboard
- Multiple SRS Fault Codes Present In Diagnostic Readout
- After An Accident, The Unit Shows Crash Data Or Permanent Faults
- Intermittent Airbag Faults Following Water Exposure Or Electrical Repairs
Keywords: Airbag Control Unit, Airbag ECU, SRS Module, Citroën C4, 9653493780, 603726100 — ideal for workshops and experienced DIY mechanics searching by part number.
