Why would the engine-motor light start flashing on the dash of my 2003 Holden Rodeo Turbo Diesel Ute and Why cant I start the Ute When this engine-motor Light is Flashing Its Not the Glow Plug either.?

I don't know what YOUR vehicle does specifically, but most diesels have "glow plugs" that come on when the engine is cold. The glow plugs warm a spot in the cylinder making the engine start much more easily, especially in cold weather. I can't speak for YOUR engine, but in general, there is usually a light on the instrument cluster that flashes while the glow plug is heating. Once the glow plugs are up to temperature, the light stops flashing and you can start the engine. If there is any doubt, read the section of the owners manual that describes the operation of the glow plugs.