Can anyone help, I am tring to find out where the 4 wires which connect to the immobiliser transponder on the ignition switch go to? I've got an intermittent starting issue that I've traced to the immobiliser system  its either a faulty transponder or a damaged wire from the transponder and want to continuity test of the 4 wires but once they join the wiring loom and go down into the steering column area I don't know where they terminate, I can't find out off electrical schematics. any help would be appreciated.

What colours do you have ?

I would suggest that one would be a supply, possibly 12V+ (or 5V regulated), a second would be earth/ground 0V, and the other two would go to the ECU as a control signal.  There is a possibility that all four cores do go to the ECU, and getting at the ECU end, which is protected by tamperproof screws may not be easy.....

28 minutes ago, Paulkp said:

What colours do you have ?

I would suggest that one would be a supply, possibly 12V+ (or 5V regulated), a second would be earth/ground 0V, and the other two would go to the ECU as a control signal.  There is a possibility that all four cores do go to the ECU, and getting at the ECU end, which is protected by tamperproof screws may not be easy.....

Thanks paulkp, I'm not with the car just now so can't say what color the wires are. I assume that the ECU has push fit connectors to it as opposed to being hard wired so if I could disconnect the relevant connector this would give me access to both ends of the wires that I'm interested in. Any idea where the ECU is located on this model?

ECU is the grey slab fitted to the battery box, just behind NS headlight, and it has a single multi way connector, held on by the aforementioned tamperproof screws....

Make sure adjacent earth points are good, and it has been suggested that there is an ECU earth direct to the -ve connector on the battery which could cause unusuall problems.

Read Coil : Multiway

Pin 1  12V from F12

Pin 2  SW/GN Pin F17

Pin 3  WS/GN Pin F29

Pin 4  BR/GN Pin F28

This information is gleaned from the combination of Fusion and Fiesta Diagrams I have, but may not be absolutely correct for your vehicle.

I would think the code in the key, is matched with the ECU itself, so if you can find a read coil from a scrappy, you might be able to swap them out for a test.

How many keys do you have ?

Good Luck!

Good info paulkp, thanks. I've got two chipped keys, both give the same problem which why I think its an issue with the reader or wiring, I'll check the wires first them the transponder, fingers crossed it's just one or the other. Ta