I have a 2002 x type 3.0 and some time when I attempt to start the car it will not turn over. There is a lot of clicking noises and the gearbox fault message appears, also all of the gauges except the fuel gauge stops working and every light on the dash appears. Also the traction control light is blinking. I removed the CPU and notice there was some rust on it and also on the inside of the metal case. The car starts some days but not others does anyone know what could be the problem? I figure it's an electrical issue I'm just not sure where to look

 

Sounds like you kind of answered your own question. If there is rust present that mean there was moisture intrusion. Try and clean up the rust if you can on any components and contacts as best you can and try and find the source of the moisture and eliminate it.

You might also check the battery and the battery cables as well.