Peugeot 307 2.0 Hdi Dec 2005 Electrics

Hello all here is my story
Driving along all working then anti pollution fault light comes on in centre of dash display and engine symbol light on instrument cluster, speedo etc, car immediately looses power and then stops.
Then it will turn over but not fire.
Like its been imobilised.
Twice now its done that and started the next day and twice its taking us playing with the wiring but no clue what we did exactly.
It just started eventually.
With no faults showing.
Only fault that comes up when not starting is a door disarmed message.
This makes the car quite useless and dangerous in some circumstances.
If you can make any suggestions it will be appreciated. Cheers.