Steve is right, Stability control has nothing to do with the engine. Pecus is not a registered fault code. Are you sure you are reading the code right? You need to have a scan of your emission control fault codes on OBD 2 diagnostic system. This will give you an accurate analysis of what is wrong. I am assuming that Jags in the UK have an on board diagnostic system. Maybe that is why Pecus does not mean anything on this side of the ocean. What kind of diagnostics does the XJ300 offer in the UK? In order to proceed without a diagnostic scan, use the old fashioned method. Ascertain if the spark plugs are getting spark by the "look at the spark plug end of the wire" method while trying to start the engine. Find out if you are getting fuel pressure at the input to the fuel rail by slightly opening the pipe connector and cranking the engine briefly. This should cause a very noticeable squirt of petroleum. Dont do this too long since you do not want to start a fire. Just a couple of seconds. Let me know what you find out. If you start an engine fire, dont bother to call back. You will have bigger problems.