420A 2gNT Harness and computer problem

[Dannyreed14141414]

So I'm new to these cars. I save both of them from sitting my 97 Eclipse GS and my 96 Eclipse.

So the 97 GS is the one that started up right away with a Lil love well I recently started having trouble with the transmission slipping so immediately started thing replace it well I hooked my code reader uo and I was throwing a bunch of codes for the tranny a couple short circuit or sum thing and shift solenoid e.

So as I'm going of all the plugs and wires and connections I notice when I pulled the two main plugs out of the computer on the driver side engine by I found the top plug full of looked like oil. So I cleaned it out and then took the plug on the harness apart cleaned everything and hooked it up then when to start it fired up well took it for a test drive shifted perfectly one code for o2 sensor that's not plugged in so I'm thinking perfect.

Well next morning I started it check engine light throwing ten different codes. Where do I start?