C5 Immobiliser Fault

[xantom]

Hi guys, this is actually a new post but I can't seem to work out how to make a new post. Given up trying and hope someone reads this.
I've been brought home courtesy of Green Flag again. Stopped late on Saturday near Leicester for a quick nap on return to Lincoln from dropping number 3 son off at Heathrow for his return to NZ. Wife phoned and snapped me out of doze and I went to start car. Energetic turnover but no start.. After about 3 goes I got an Immobiliser Fault indication. Wife picked me up and I returned to the car on Sunday to try it, hoping quite irrationally that it might just start. It didn't. Excellent Green Flag provided mechanic called Stig tried intelligently for ages but couldn't get her to fire up so up onto the trailer she went.
All fuses have been checked: battery is new and charged: fuel pump buzzes on ignition. Stig's diagnostic kit said key being recognised so reckons it's something further into the system like the immobiliser's ECU.
Now the car is in Economy Mode and I can't lower the driver's window even to try a proper BSI reset.
Does anyone know how I might get the driver's window down while the car's in Economy Mode? Then I can at least try a full, properly done BSI reset as my last resort before having to consider the drastic step of asking Citroen for help.
Thanks,
Tom

[GiveMeABreak]

For now, get in the car, shut the doors, put the key in and turn to ignition position, hold down lock button on fob for 10 seconds without letting go. Remove key and try locking and unlocking doors with remote. Then put key in and try starting.

To start a new post, go to the Citroen section to the left of the Most Liked Posts Grey Banner you will see a button that says NEW TOPIC. Click that and give your post a title and away you go.

[xantom]

Thanks Marc, I'll try that, and thanks for the post advice; don't know how I missed that.
Tom

[xantia_v6]

I have split and moved this topic to the correct place on the forum

[wheeler]

Have you tried using your spare key ?
You don't need the window down to do a BSI reset. I wouldn't recommend even trying to get it down when the car is in eco mode incase you cant get it back up.
Do you have access to lexia/diagbox ?
Do you have the immobiliser security code ?
If the BSI reset doesn't work you will likley need these before going any further.