The BSI is the Body Control unit (ECU) and the fuse box in the glovebox of the Citroen C3.
The BSI controls many of the electrical functions and often arbitrates between the switches and the devices they operate.
If you change the car battery or have strange electrical problems you may first wish to RESET then C3 BSI by following this procedure before exploring further.

Resetting the BSI computer:

Open the drivers window and the bonnet.
Close all the doors, switch off everything, like the radio, phone charger etc.
Remove the ignition key via the open window
WAIT 10 minutes
Disconnect the battery.

(change the battery at this point if this is required, otherwise WAIT 30 seconds)

Reconnect the battery,
WAIT 1 minute
Keeping the doors closed, lean in via the drivers window
Switch on the 'ignition' (Don't start the engine)
Switch on lights (Dipped, normal driving lights)
WAIT 30 Seconds
Start the car



If you need to replace the BSI (fusebox) you can fit a used one, but it must also come with the correct engine ECU and the Keys as a complete kit for everything to work


You may also need to do this: Reset the electric windows on a Citroen C3

Regards