well i was driving home last night and all of a sudden my light went out on my dash, so i couldnt see how fast i was goin. it turns out i blew a fuse some how. that problem is fixed. but i was i was under my steering colum and found a green plug that was unplugged. so i plugged that back together thinking that would fix my dash/gauge cluster lighting problem, then i proceeded to turn my car back on hoping my lights would turn on. but nothing happened... then all of a sudden my car started to idle funny and i got a check engine light. then i was great what the hell did i do. then i wanted to see if what would happen if i unplugged it, so i unplugged and my cars idle was fine and the check engine light went away. can anybody tell me what this plug is for.

 

bump

 

The green plugs are for use by the dealer during PDI and for diagnostics. They are supposed to be left unplugged. If you plug them together the ECU is placed into a diagnostic mode where the CEL flashes continously and various relays/solenoids are cycled, also the fans will cycle on and off.
Unplug them and leave them alone.

 

yeah i unplugged them.