Ok, I took out my ECU to find out what number it was, but for all the information I found, I am at a loss for what the "extra" plug is for. This picture and all others I found only show 3 connectors, but mine has all four. What is the fourth one for?

*borrowed from http://www.markl.f9.co.uk
My fourth one is obviously where the blank one is on the picture. Any ideas. I searched here, and google for hours, and I have no idea.
btw, I have a 98 civic lx auto 4dr as in my sig.
elevtro

 

its an obd2 ecu, and the extra plug with pins is for the automatic

 

Thanks for the info BSeriesTurbo.