Citroen c3 2003 1.4, engine wont turn off

Hi Guys

I have a citroen c3, turn key off engine still runs, dash stays lit, stall car dash lights go out after 5 seconds.

Have disconected ign switch still same
no fault codes
when ign turned off (engine still running) BSI looses voltage (according to live data)

Any Help appreciated
Regards
Dave Williams