I presume your talking about a TD5!
With the bonnet open, take the battery cover off on the driver side, under that cover you will see the battery,vehicle jack and behind that slotted in is the ECU, if memory serves theres a screw holding it in, if so remove the screw and slide the ECU out and remove the two large multi plugs and inspect for oil.
If oil is found, clean out with contact cleaner spray as a temporary measure and replace the injector loom, I would advise getting a genuine one and theres plenty of "how to's" around explaining how to replace it.
Hope that helps.
Chris