Hello, and thank you for allowing me the opportunity to help you. If I am not online when you are, please allow me time to return. You need to start with a voltage drop test of the ignition switch. It is common for the ignition switch to fail internally and cause little to no voltage to get to the computer or various relays which will cause this. Do you know where this is located?
Sorry for not getting back to you sooner, but vehicle is out of town. Cannot test until client brings vehjcle back to workshop. Your suggestion confirms what I suspected. Incidentally, engine size is 2.7 Litres, not the 2.3 that I initially said. Will be in touch when I am able to test for voltage drop. Thank-you for your help so far.