Peugeot, Citroën and DS BSI failure: symptoms and fixes

The BSI is the body computer on Peugeot, Citroën and DS cars. Because it runs so many functions, a BSI problem can look like a dozen different faults. Many are fixable on the board.

Typical symptoms

• Central locking not working, or doors locking by themselves.
• Wipers, horn or lights stuck on, or not working.
• Warning messages and random electrical faults.
• No start with an anti-theft message after the BSI was swapped.
• Dead BSI after a flat battery or water leak.

Check first

• Battery condition — low voltage causes many BSI symptoms.
• Water ingress around the BSI (it sits under the dashboard on many models).
• Fuses and relays in and around the BSI.
• Wiring to door locks and wiper motors — a shorted motor can damage BSI drivers.

Repair or clone?

• Relay, driver or corrosion faults on the board can usually be repaired, keeping your original BSI.
• If the BSI is beyond repair, a second-hand BSI with the same part number and version needs your original's data transferred so it recognises your keys and engine ECU.
• Send us a photo of the BSI label (all numbers) and we'll confirm which route applies.

Questions

Can I fit a used BSI without programming?

Not on its own. The used BSI has another car's immobiliser data. Cloning your original's data into it makes it work with your car in most cases.

Related services

BCM / BSI / body module cloning · Control module & PCB repair

General guidance only — always diagnose the vehicle properly.