if P0605 really means 'flash rom cpu abnormality'.....
brings up LOTS of questions....
1) does this ECU control the display, that shows you the error code ?
2) if not HOW does the 'error code' get transmitted from ECU to the display ?
If #1 is true, then the 'known good' ECU would have 'cleared' the error code< well, actually it would not be IN the ECU,so can't be displayed.
Also if #1 is true , then power ( +12 and gnd ) are good as ECU IS functional..it's displaying information.
Since the 'known good ECU' gave the EXACT same code, it's NOT the $$$ ECU, but the error code 'suggests' it IS an 'internal' problem INSIDE the ECU, making it 'bad', but the 'known good ECU' says the same thing....so it must be 'bad' but it's a 'known good ECU'.......arrrrrgh.
Sadly ONLY the original programmer KNOWS why that P0605 came up.