The CAS is located at the front of the engine, taking its readings from a reluctor ring, mounted onto the crank pulley. There are two different types on the XJ40. The older, ‘Fat’ connector and the newer ‘Slim’ connector. The Fat item is no longer available, new. You need to solder the fat connector to a slim connector sensor. In my case, I was able to source a brand new ‘Fat’ connector sensor. Failure of the sensor results in a no start condition, difficulty to start when warm and/or misfires across the rev range.