The white residue is tin plating that has oxidized. When you see green, the brass terminal beneath it is corroding.
AC condenser drain is the main cause of this. The drain either breaks or clogs, funneling water onto the molded grommet - then gravity does the rest, channeling water directly into the ECM. Electrolysis occurs since there are several grounds within the harness connectors, along with positive signals. Major corrosion ensues....
If the connectors were on the bottom instead of the top, you'd never see that kind of problem.
No-start is common when the Orange MEM feed wire terminal, C16, corrodes out completely. I've seen it happen several times over the years.
Time for a new connector pigtail or terminal/connector replacement, and replacement ECM. You can't fix it by cleaning and spraying with tuner cleaner - once the tin plating is corroded off, it must be replaced.