u cannot just pull plugs out of the box to your right, that is the door lock relay unit not the immobiliser, the immobilser is built into the ECU and will have to be bypassed there by finding the correct cable/s and bridging them out with a permanent 12V+ supply, the light on the dash will remain permanently on but the immobiliser is also completely bypassed.
hope this helps as have had same prob on 1993 1.6i lx escort.
The reason for the fault is there is a mapping unit behind the ignition and this does fail sometimes but it is cheaper and easier to bypass the immobilser.
A J
September 2005