2006 Fiesta ST High Engine Temp Error even when car is ice cold

Hi All,

Yesterday my ST started behaving oddly, the weirdest part of it all is that the car wasn't behaving oddly at all...

I drove from a roadworthy station (recently bought the car and needed to have new roadworthy test done) car was 100% fine, stopped at a garage, got it filled up. When I wanted to start it again I got the flashing red light, and a High Engine Temperature Error message, after that I got the Engine System Fault error. Exactly like in this video Youtube Video showing errors https://www.youtube.com/watch?v=6iYZIE121VA, I noticed that the heat gauge had not moved at all and the car was on 90 when I turned it off, I then checked in the test menu and there was no reading for engine temp, just "-------", I also noticed that engine rpm, which usually says 0 was also showing "---------". The 2 DTC codes shown from that menu are C100 and E510...

I then had the car towed home and tried again later, the car was cold at this stage but still gave the same High Engine Temp error so I left it over night. Got to the car in the morning, put the key in it, no error and started 1st time, I let it get to temp, turned it off and back on, no problem at all, 20 minutes later, took it for a drive around the block, car drives 100%, stopped at home, turned it off, tried to turn it back on and the error is back, wont allow you to start the car.

So I then got hold of a OBD2 scanner so I can pull the code from the car but the scanner wont connect to the ecu, the scanner supports 13 protocols including CAN 11 bit, which is what I've been told the Ford uses. I then tested the scanner on my wifes VW and it work perfectly. This got me thinking that the ecu might be dead or not getting power. I'm leaning towards the latter as the car has started and ran flawlessly after giving the error the 1st time. I unplugged the ECU just to check what it does and it still behaves exactly the same way even with the ECU unplugged.

Not really to keen on taking it to a dealer cause they generally know no more than a hour on google will teach you. Any advice on what to check would be much appreciated.
I've tried several OBD scanners with my fiesta and Forscan on an iPhone and the only one I've gotten to work has both HS-can and MS-can and a little toggle switch to go between the two. That could work to at least interface with the computer and see what it's saying. Otherwise, its probably either a bad PCM, bad ECT sensor, or bad CHT sensor I would think.