This airbag control unit (SRS ECU) is designed for the Citroën C4 first generation and is identified by the listed part numbers. It is intended primarily for professional workshops and experienced DIY mechanics who search parts by product code. The unit monitors crash sensors and controls airbag and seatbelt pretensioner deployment to protect vehicle occupants in the event of a collision.

Key Benefits

• Direct replacement for original Citroën SRS control units, simplifying repairs when part numbers match.
• Compact, vehicle-specific design ensures correct communications with airbag sensors and safety restraints.
• Allows re‑establishment of SRS functionality after removal and correct initialization.

Technical Information

• Manufacturer: Stellantis (Citroën)
• Model: Citroën C4 I (First Generation)
• Product Codes: 9662643680
• Other Numbers: 603725800, 654633, 654634

Compatible Models

Citroën C4 First Generation (C4 I), model years approximately 2004–2010. Compatibility depends on equipment level and the exact part number — customers commonly locate this unit by the listed codes.

Installation Recommendations

• Always disconnect the vehicle battery and wait at least 10 minutes before starting work to allow SRS capacitors to discharge.
• Access the unit carefully—SRS control units are typically located inside the passenger compartment, often beneath the center console or under the front seats; remove trim panels without forcing clips.
• Handle connectors by the housing, do not pull wiring; ensure locking tabs are fully disengaged before separation.
• After mechanical installation, use a compatible PSA diagnostic tool (for example DiagBox/Lexia) to perform SRS system checks, clear fault codes and complete any required initialization or coding.
• If the unit stores crash data from a prior deployment, professional erasure/initialization with diagnostic equipment will be necessary before returning the vehicle to service.
• Observe manufacturer torque settings and assembly order for trim and fasteners to avoid rattles or damaged clips.

Replacement Procedure (Overview)

General replacement steps: disconnect the battery and wait; remove relevant trim to reach the SRS unit; unplug connectors and remove mounting fasteners; fit the new unit, reconnect connectors and fasteners; reconnect the battery and run diagnostic checks to confirm SRS system status and clear any stored faults. Always follow the vehicle manufacturer service manual for safe working procedures.

Why The Part Most Often Fails

• Activation During A Collision: Deployment of airbags records crash data and often requires module replacement or professional reinitialization.
• Water Ingress And Corrosion: Moisture or fluid leaks into the cabin can corrode connectors and printed circuit boards.
• Electrical Events: Voltage spikes, incorrect jump-starting or problems with charging systems can damage the unit.
• Connector Or Wiring Damage: Broken pins, poor repairs, or mechanical strain lead to intermittent faults or loss of communication with sensors.

Notes For Workshops And Mechanics

When sourcing replacement SRS control units, match the exact part number to reduce diagnostic time. After installation, verify full system operation with a diagnostic scanner and follow safety rules when working around airbag components. If you are not equipped to perform SRS reinitialization, consult a qualified technician with PSA-compatible diagnostic equipment.

This airbag control unit (SRS ECU) is a direct-fit module designed for the first-generation Citroën C4. It is suitable for professional workshops and competent DIY mechanics who service SRS systems. The unit restores or replaces the vehicle’s airbag system control, resolving persistent airbag warning lamps or failures caused by prior deployment, electrical faults or physical damage. Common reference numbers for quick searches are included below, improving findability for technicians searching by part number.

Technical Information

• Manufacturer: Stellantis (Citroën)
• Model: Citroën C4 I (First Series)
• Product Codes: 9662643980, 603726100
• Additional Numbers: 654635, 654636

Function and Application

The airbag control unit (also referred to as SRS control module or airbag ECU) continuously monitors crash sensors, seatbelt pretensioners and airbag squibs. In the event of a detected collision, the unit triggers deployment of safety restraints. It also stores fault codes and crash event data used by diagnostic tools. This unit is intended for use in Citroën C4 first-series vehicles; always confirm the part numbers against the vehicle’s repair data when fitting.

Replacement Procedure (Overview)

• Park vehicle on level ground and remove key from ignition.
• Disconnect the negative battery terminal and wait a minimum of 10 minutes to allow system capacitors to discharge.
• Access the SRS control module location (typically inside the passenger compartment; exact placement varies by equipment level and production date).
• Carefully disconnect SRS connectors—do not pull on wiring, release locking tabs first.
• Unbolt and remove the old unit, install the replacement, tighten fasteners to manufacturer torque, and reconnect connectors securely.
• After installation, clear SRS fault codes and perform an SRS system check with an appropriate diagnostic tool to ensure the airbag warning lamp is extinguished and no stored faults remain.

Installation Recommendations

• Observe all SRS safety precautions: wear appropriate PPE, avoid static discharge and never probe airbag connectors with an energized circuit.
• Always disconnect the battery before working on the SRS system and follow the vehicle manufacturer’s removal/installation sequence to prevent damage.
• Use a diagnostic scanner capable of reading SRS fault memory and performing system initialization after replacement.
• If the vehicle has been in a collision, inspect associated wiring, crash sensors and pretensioners; replace any components that show signs of damage or corrosion.
• If in doubt, have the final checks performed by a qualified technician with SRS experience and diagnostic equipment.

Most Common Failure Reasons

• Collision deployment events—modules often become nonfunctional after airbag deployment.
• Water ingress or corrosion affecting connectors and circuit board traces.
• Electrical faults from short circuits, improper jump-starting or incorrect handling during battery disconnection.
• Physical damage from impacts or improper prior repairs.
• Stored crash data or persistent fault codes preventing normal operation and illuminating the airbag warning light.

Notes for Buyers

Part numbers commonly used to locate this unit: 9662643980, 603726100 (additional references 654635, 654636). This description reflects the item’s intended application for Citroën C4 first-series vehicles and is aimed at mechanics and experienced DIYers searching by part number. The unit is described as fully functional in the original listing.

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.

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:

1. Disconnect the negative battery terminal and wait at least 10–15 minutes to discharge residual power in the SRS circuits.
2. Locate the unit (position varies with trim—commonly mounted under the centre console, beneath the passenger seat or behind the glovebox).
3. Remove necessary trim panels and secure fixings to access the control unit.
4. Carefully unplug the electrical connectors; avoid pulling on wiring and protect connector latches.
5. Unbolt the unit, replace with the new unit and reconnect connectors, ensuring a firm fit.
6. 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.

Typically, the airbag unit can fail due to factors such as electrical faults, vehicle collisions, or degradation over time. Regular checks are recommended, particularly if the airbag warning light is illuminated on your dashboard. Replacing this unit can significantly enhance safety and ensure proper deployment of airbags during a collision.

To replace the airbag unit, first, disconnect the vehicle’s battery to avoid any accidental deployment. Carefully remove any surrounding trim and access the unit, which is generally located beneath the dashboard. Disconnect the wiring harnesses and remove the unit from its mounting. Install the new unit by reversing these steps, ensuring all connections are secure.

Technical Information:

• Manufacturer: PSA Group
• Model: Citroën C4
• Product Codes: 9658137980
• Additional Numbers: 603 72 58 00

This original equipment airbag control module (SRS ECU) is a direct-fit replacement for vehicles equipped with the Citroën C4 airbag system. Designed to manage deployment logic, monitor crash sensors and store event data, the unit restores proper SRS functionality when the original module is damaged or shows fault codes. Ideal for professional workshops and experienced DIY mechanics searching by part number (9662643980 / 603 72 61 00), this module helps return the restraint system to safe, working order when handled and installed correctly.

Technical Information

• Manufacturer: Stellantis / Citroën
• Model: Citroën C4 (1st Generation)
• Product Codes: 9662643980
• Other Numbers: 603 72 61 00

Applications

Commonly used on Citroën C4 first-generation models. The part is often referenced by the product code 9662643980, which is a key search term for technicians and parts buyers.

Function And Symptoms

The Airbag Control Unit (SRS ECU) continuously monitors impact sensors, seat belt buckle switches and crash signals and decides if and when to trigger airbag inflation. When the unit records a collision event or detects internal faults, the airbag warning light will remain illuminated on the dashboard. Symptoms of a failing module include persistent SRS warning lamp, stored crash data, loss of communication with diagnostic tools or intermittent fault codes related to the restraint system.

Most Common Failure Reasons

• Post-collision status: After an impact the module often records crash flags and disables further deployment until data are cleared or the unit is replaced.
• Water Ingress Or Corrosion: Moisture or corrosion on connectors can cause electrical faults and loss of communication.
• Electrical Disturbances: Short circuits, jump-starts or voltage spikes may damage internal electronics.
• Connector Damage Or Mechanical Stress: Improper removal/installation or damaged harnesses can lead to faults.

Replacement And Installation Recommendations

Only perform replacement if you are qualified and follow safety procedures. General replacement steps used by professionals:

• Disconnect The Battery: Always disconnect the negative battery terminal and wait at least 10 minutes (some manufacturers recommend longer) to allow capacitors to discharge before touching the SRS system.
• Locate The Unit: The airbag ECU is typically mounted inside the passenger compartment (under the dashboard, behind the glovebox or under seats depending on model). Verify location on the specific vehicle before removal.
• Handle With Care: Avoid static discharge and do not open or attempt to repair the module. Remove mounting bolts and disconnect connectors gently.
• Install And Secure: Fit the replacement unit, reconnect all connectors firmly and secure mounting hardware to manufacturer torque specifications.
• Diagnostic Check And Clearing Crash Data: After installation, perform diagnostics and clear any crash data or SRS fault codes using an appropriate diagnostic tool compatible with PSA/Stellantis systems (e.g., DiagBox). Final system verification should confirm the SRS warning lamp extinguishes and that no new faults are present.

Advice For Professionals And DIY Mechanics

This module is intended for users familiar with vehicle safety systems. Always follow the vehicle manufacturer’s procedures for SRS work. If crash data are present, the unit may require erasure and system initialization with a compatible diagnostic tool. Incorrect handling or installation can compromise occupant safety—when in doubt, seek a trained technician.