Description
BSM B4 SIEMENS Citroën Peugeot for vehicles Citroën C2, Citroën C3, Berlingo, Xsara, Xsara Picasso and Peugeot 206, 307, 406, Partner. This is a used part with a guarantee of functionality. Some mounting brackets may be damaged — this does not affect functionality.
The BSM B4 (Boîtier de Servitude Moteur) manufactured by Siemens is the engine bay service box / body control module used on a range of PSA vehicles. It centrally distributes power to fuses and relays and manages several vehicle functions such as immobilizer interface, central locking, lighting circuits, wiper control, and certain comfort/electrical circuits. For professional mechanics and experienced DIY technicians this unit is a direct replacement option when the original module shows electrical faults or partial failures.
Key Features And Benefits
– Direct fit for listed Citroën and Peugeot models. Optimised for original wiring harness and connectors.
– Controls multiple electrical circuits from a single module, reducing the number of separate relays/fuses in the engine bay.
– Sold as a used unit with functional guarantee — a cost-effective alternative to new OEM units.
Compatibility
- Citroën C2
- Citroën C3
- Citroën Berlingo
- Citroën Xsara
- Citroën Xsara Picasso
- Peugeot 206
- Peugeot 307
- Peugeot 406
- Peugeot Partner
Technical Information
- Manufacturer: Siemens
- Model: BSM B4
- Product Codes: 9650618380, 9650618380-00
- Other Numbers: T118470004, L 6500Y3, 6500Y1, 6500.Y1., 6500.Y3
Installation Recommendations
– Always disconnect the vehicle battery before starting work to avoid short circuits and damage to the module.
– Remove the engine bay trim or cover to access the BSM. Unclip and label wiring connectors if needed to avoid confusion during reassembly.
– Carefully release the module from its mounting points; note that some plastic bracket tabs on used units may be damaged without affecting electrical function.
– Replace the unit, reconnect all connectors firmly and reattach all mounts. Reconnect the battery and verify basic functions (lights, central locking, instrument cluster warning lights) before returning the vehicle to service.
– If symptoms relate to immobilizer, key recognition, or persistent fault codes, professional diagnostic and coding tools for PSA (DiagBox/Lexia/PP2000) may be required to reinitialise or adapt the module and keys.
How The Part Is Replaced
Typical replacement is straightforward for a trained technician: 1) Disconnect battery negative. 2) Remove protective covers and locate the BSM in the engine bay. 3) Unplug connectors and remove the module from its bracket. 4) Install the replacement unit, reconnect connectors and battery. 5) Check electrical systems and clear any fault codes with a diagnostic tool. Allow extra time if coding or key adaptation is necessary.
Why This Part Fails Most Often
Common causes of BSM failure include water ingress or moisture in the engine bay, corrosion on connector pins, thermal stress and ageing of solder joints, electrical surges or poor battery connections. Mechanical damage to external mounting tabs is frequently observed on used units (this normally does not affect electrical performance). Failures typically manifest as intermittent or total loss of functions controlled by the module: central locking not responding, immobiliser/warning lights, non-functioning lights or wipers, blown fuses, or failure to start.
Notes
This unit is supplied used but guaranteed functional. Some external brackets may be damaged cosmetically; functional operation is not affected.
