From S-Chassis.com Wiki
ECU (or electrical plug) Pinouts are a diagrams used to identify the function and usually color of each slot or wire in the electrical plug. The diagrams consist of a number layout of the plug followed by a chart to give the function and color of each associated numbered pin on the plug.
The most important thing to know about reading these diagrams is that they are read from the rear of the plug. This is the side the the wires are inserted into rather than the side facing the ECU or connector. Another way to picture this is to imagine you are looking at the pins on the ECU itself.
Start by holding the plug looking at the wire side and align it as shown in the picture. Most plugs are not symmetrical side to side or vertically. Correspond this information with that on the diagram to align. In the rare case you have a perfectly symmetrical plug in which you cannot align it based on shape, rear the diagram for wire colors and align as such.
Once Aligned, find the particular function and corresponding pin number on the diagram that you are searching for. Look for its position on the diagram and count over on the plug in your hand to find the wire. Do not forget to count black slots as even they have an associated number. If available, verify with wire color to double check your selection.
