This Airbag Control Unit (SRS Module) is a direct-fit replacement for Citroën C4 Picasso vehicles and is ideal for professional workshops and experienced DIY mechanics. Designed to manage crash detection, airbag deployment and restraint system diagnostics, this unit restores proper SRS functionality after replacement. Commonly searched by OEM reference numbers (e.g. 9665396680, 9673625180, 6546H9), it is suitable for cases where the original module is defective but the vehicle wiring and sensors remain intact.

Technical Information

• Manufacturer: Stellantis / Citroën / Peugeot
• Model: Citroën C4 Picasso
• Product Codes: 9665396680, 9673625180, 610955800, 6546H9
• Additional Numbers: 6546J0, 6546T1, 966539680, 9673625180

Fitment

Intended for Citroën C4 Picasso models equipped with the corresponding SRS system matching the listed part numbers. Verify part references against the label on the original unit before fitting.

Function and Benefits

The Airbag Control Unit continuously monitors crash sensors, seat belt pretensioners and airbag circuits. On detecting a collision event it triggers deployment of the appropriate restraint components and logs crash data and fault codes. Replacing a faulty unit restores SRS diagnostics, clears permanent airbag faults (when underlying issues are resolved) and ensures the vehicle can correctly respond in a crash.

Common Failure Causes

• Activation during a collision (module stores crash data and may be locked out).
• Electrical damage from short circuits, jump-starts or battery voltage spikes.
• Corrosion or poor connector contacts due to moisture ingress.
• Physical damage from improper handling or impact to the mounting area.
• Software/firmware corruption or internal electronic faults.
• Faults in related sensors or wiring that cause persistent SRS errors.

Replacement Procedure (Overview)

Recommended for experienced technicians or skilled DIYers. Typical replacement steps:

• Disconnect the vehicle battery and wait at least 10 minutes to ensure SRS capacitors discharge.
• Remove trim panels and seats as required to access the unit (usually mounted under the center console or behind the dashboard).
• Unbolt the module and carefully disconnect all electrical connectors—avoid pulling on wiring.
• Install the replacement unit, secure mounting bolts to manufacturer torque, and reconnect connectors.
• Reconnect the battery and use a diagnostic tool capable of SRS functions to clear stored fault codes and run system checks.

Installation Recommendations

• Always disconnect the battery before beginning work and follow the vehicle manufacturer’s safety procedures.
• Handle the unit carefully; avoid static discharge and mechanical shock to the module.
• Use a diagnostic tool with SRS capabilities (DiagBox/Lexia/PP2000 or equivalent) to clear errors and verify system status after installation.
• If the airbag warning lamp remains on after replacement, inspect wiring, crash sensors and seat belt pretensioners—address underlying faults before assuming the module is faulty.
• Record and retain any crash data as required by local regulations when replacing a unit that has recorded a deployment event.

Why This Part Fails Most Often

Airbag control units most commonly fail after a collision (deployment event) or due to electrical damage such as corrosion, water ingress or voltage spikes. Harsh repairs, incorrect reconnection or prolonged exposure to moisture can also degrade internal electronics. Replacing the unit without addressing the root cause (damaged sensors, corroded connectors or wiring faults) will often result in persistent SRS warnings.

Notes for Buyers

Unit is supplied as described: fully functional. Check the part numbers on your original module to ensure match. This product is aimed at professional mechanics and experienced DIYers familiar with SRS safety procedures and diagnostic equipment.

Product Overview

This airbag (SRS) control unit is a direct-fit replacement for Citroën C4 Picasso models and is often sought under part numbers 9664217980, 603474700, 6546A8 or 6546A9. Designed to monitor impact sensors and manage airbag deployment, the unit is essential for vehicle occupant safety. Ideal for professional technicians and experienced DIYers who search and order parts by product code.

Technical Information

• Manufacturer: Stellantis / Citroën / Peugeot
• Model: Citroën C4 Picasso
• Product Codes: 9664217980, 603474700, 6546A8
• Other Numbers: 6546A9, NFP

Function

The SRS control unit Continuously Monitors Crash Sensors, Seatbelt Buckle Signals And Airbag Circuits, Decides When To Trigger Airbag Deployment And Stores Crash-Related Fault Data. It Communicates With The Vehicle Network To Coordinate Restraint Actions And To Illuminate The Airbag Warning Light When A Fault Is Present.

How Replacement Works

Replacement Requires Careful Handling: Read And Record Fault Codes Before Removal, Disconnect Battery And Wait To Allow System Capacitors To Discharge, Remove Interior Trim To Access The Unit, Unplug Connectors And Replace Mounting Hardware. After Installation Clear Fault Memory And Perform Full SRS System Checks With A Diagnostic Tool To Confirm Proper Operation. If The Unit Contains Crash Data From A Previous Deployment, It May Be Ineligible For Reuse.

Installation Recommendations

• Always Disconnect The Negative Battery Terminal First And Wait At Least 10 Minutes Before Working On The SRS System.
• Locate The Unit Carefully — Depending On Trim Level It Is Typically Mounted Under The Center Console, Under The Front Passenger Seat Or Behind Interior Trim Panels.
• Use Correct Tools And Torque Values For Fasteners; Protect Connectors From Dirt And Corrosion During Reassembly.
• Use A Professional Diagnostic Tool To Read/Clear Faults And To Perform Post-Installation SRS Tests; Verify That The Airbag Warning Light Is Extinguished.
• If Uncertain About Procedures, Seek A Technician Experienced With Citroën Safety Systems.

Why The Part Most Commonly Fails

Common Failure Causes Include Crash Deployment, Water Ingress Or Moisture Damage, Corroded Or Loose Connectors, Electrical Surges Or Short Circuits, And Internal Component Degradation After Long Service Life. Many Units Become Non-Functional After An Accident Due To Stored Deployment Data Or Internal Damage.

Additional Notes

This Unit Is Frequently Located By Its Part Number During Sourcing. Ensure The Part Number Matches Your Vehicle’s Requirement Before Installation. Proper Diagnostic Verification After Fitting Is Essential For Safety And Roadworthiness.