Hi Nick, even on fords own wiring diagrams you will not find a diagram of the immobiliser circuit!!! for security reasons? but there are some fuse's you can check in the central fuse box by your right knee fuse's 13&19 and in the battery fuse box (back right side as you look under bonnet) fuse's 23,32,35,36&40 all of these fuse's are connected with the PATS (immobiliser) dependant on model and year, some are also to do with the memory of the ecu and the radio code memory so if you pull the fuse's out to check them you will need your radio code( if you dont have the code? if its a standard ford unit give me the serial no M654321 and I will give you the code) and when you get the engine started it will not drive as normal for the first 20 miles whilst the ecu re-learns its settings??
Hope this helps
nige110162@hotmail.co.uk
nigel
December 2007