2005 Vauxhall Vectra warning light

You using correct key ? It indicates immobiliser fault . This is from owners manual

Control indicator for immobiliser
If control indicator o lights when the
ignition is switched on, the key is not
recognised by the system and the engine
cannot b e started:
1. Turn key to 0 in the ignition a nd remove.
2. Reinsert key in ignition switch.
3. Then repeat starting procedure.
If the control indicator o remains lit, try to
start the engine using the spare key and
consult a workshop. We recommend a
Vauxhall Authorised Repairer.
If the control indicator flashes whilst the
ignition is on A, there is a fault in the
engine electronics. The engine cannot be
started – see page 166.
Note
The immobiliser does not lock the doors.
Therefore, after leaving the vehicle a lways
lock it and switch on the anti-theft alarm
system 3 – see pages 58, 63.
The Car Pass contains all of the vehicle’s
data and should therefore not be kept in
the vehicle.
Hav e your Car Pass on hand when
consulting a Vauxhall Authorised Repairer